Version v0.3.43 - -m Remove unnecessary calculate_checksum() calls during encryption - use filename checksum directly

.gitignore

@@ -24,3 +24,10 @@ test_truerng
 # Temporary files
 *.pad
 *.state
+
+# Downloaded dependencies (source)
+miniz/
+microtar/
+
+# Test directories
+test_dir/

Makefile

@@ -1,25 +1,40 @@
 CC = gcc
-CFLAGS = -Wall -Wextra -std=c99 -Isrc
+CFLAGS = -Wall -Wextra -std=c99 -Isrc -Isrc/miniz -Isrc/microtar
+CFLAGS_MINIZ = -Wall -Wextra -std=c99 -D_POSIX_C_SOURCE=200112L -Isrc -Isrc/miniz -Isrc/microtar -Wno-unused-function -Wno-implicit-function-declaration
 LIBS = -lm
 LIBS_STATIC = -static -lm
 ARCH = $(shell uname -m)
 TARGET = build/otp-$(ARCH)
 SOURCES = $(wildcard src/*.c)
+MINIZ_SOURCES = $(wildcard src/miniz/*.c)
+MICROTAR_SOURCES = $(wildcard src/microtar/*.c)
 OBJS = $(SOURCES:.c=.o)
+MINIZ_OBJS = $(MINIZ_SOURCES:.c=.o)
+MICROTAR_OBJS = $(MICROTAR_SOURCES:.c=.o)
+ALL_OBJS = $(OBJS) $(MINIZ_OBJS) $(MICROTAR_OBJS)
 
 # Default build target
-$(TARGET): $(OBJS)
+$(TARGET): $(ALL_OBJS)
 	@mkdir -p build
-	$(CC) $(CFLAGS) -o $(TARGET) $(OBJS) $(LIBS)
+	$(CC) $(CFLAGS) -o $(TARGET) $(ALL_OBJS) $(LIBS)
-	@rm -f $(OBJS)
+	@rm -f $(ALL_OBJS)
 
 # Static linking target
-static: $(OBJS)
+static: $(ALL_OBJS)
 	@mkdir -p build
-	$(CC) $(CFLAGS) -o $(TARGET) $(OBJS) $(LIBS_STATIC)
+	$(CC) $(CFLAGS) -o $(TARGET) $(ALL_OBJS) $(LIBS_STATIC)
-	@rm -f $(OBJS)
+	@rm -f $(ALL_OBJS)
 
-%.o: %.c
+# Compile main source files with full warnings
+src/%.o: src/%.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+# Compile miniz library files with reduced warnings
+src/miniz/%.o: src/miniz/%.c
+	$(CC) $(CFLAGS_MINIZ) -c $< -o $@
+
+# Compile microtar library files normally
+src/microtar/%.o: src/microtar/%.c
 	$(CC) $(CFLAGS) -c $< -o $@
 
 clean:

README.md

@@ -58,14 +58,14 @@ One-time pads can be trivially encrypted and decrypted using pencil and paper, m
 
 ### Download Pre-Built Binaries
 
-**[Download Current Linux x86](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.34/otp-v0.3.34-linux-x86_64)**
+**[Download Current Linux x86](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.42/otp-v0.3.42-linux-x86_64)**
 
-**[Download Current Raspberry Pi 64](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.34/otp-v0.3.34-linux-arm64)**
+**[Download Current Raspberry Pi 64](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.42/otp-v0.3.42-linux-arm64)**
 
 After downloading:
 ```bash
 # Rename for convenience, then make executable
-mv otp-v0.3.34-linux-x86_64 otp
+mv otp-v0.3.42-linux-x86_64 otp
 chmod +x otp
 
 # Run it
@@ -431,6 +431,28 @@ No.  ChkSum (first 16 chars) Size         Used         % Used
 # Select "S" for show pad info, enter checksum or prefix
 ```
 
+## Important Notes
+
+### Size Units: Decimal (SI) vs Binary (IEC)
+
+**This program uses decimal (SI) units for all size specifications**, matching the behavior of most system tools like `ls -lh`, `df -h`, and file managers:
+
+- **1 KB** = 1,000 bytes (not 1,024)
+- **1 MB** = 1,000,000 bytes (not 1,048,576)
+- **1 GB** = 1,000,000,000 bytes (not 1,073,741,824)
+- **1 TB** = 1,000,000,000,000 bytes (not 1,099,511,627,776)
+
+**Why decimal units?**
+- Consistency with system tools (`ls`, `df`, file managers)
+- Matches storage device marketing (a "1TB" USB drive has ~1,000,000,000,000 bytes)
+- Avoids confusion when comparing sizes across different tools
+- Industry standard for storage devices and file systems
+
+**Example:** When you request a 100GB pad, the program creates exactly 100,000,000,000 bytes, which will display as "100GB" in `ls -lh` and your file manager.
+
+**Note:** Some technical tools may use binary units (GiB, MiB) where 1 GiB = 1,024³ bytes. This program intentionally uses decimal units for user-friendliness and consistency with common tools.
+
+
 ## License
 
 This project includes automatic versioning system based on the Generic Automatic Version Increment System.

src/archive.c

@@ -0,0 +1,493 @@
+#define _POSIX_C_SOURCE 200809L
+#define _DEFAULT_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <dirent.h>
+#include <time.h>
+#include "main.h"
+#include "microtar/microtar.h"
+
+// Suppress warnings from miniz header
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
+#include "miniz/miniz.h"
+#pragma GCC diagnostic pop
+
+////////////////////////////////////////////////////////////////////////////////
+//      DIRECTORY ARCHIVING FUNCTIONS
+////////////////////////////////////////////////////////////////////////////////
+
+// Helper function to recursively add directory contents to TAR archive
+static int add_directory_to_tar(mtar_t* tar, const char* base_path, const char* relative_path) {
+    DIR* dir = opendir(base_path);
+    if (!dir) {
+        printf("Error: Cannot open directory '%s'\n", base_path);
+        return 1;
+    }
+
+    struct dirent* entry;
+    while ((entry = readdir(dir)) != NULL) {
+        // Skip . and ..
+        if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {
+            continue;
+        }
+
+        // Build full path
+        char full_path[2048];
+        snprintf(full_path, sizeof(full_path), "%s/%s", base_path, entry->d_name);
+
+        // Build relative path for TAR
+        char tar_path[2048];
+        if (strlen(relative_path) > 0) {
+            snprintf(tar_path, sizeof(tar_path), "%s/%s", relative_path, entry->d_name);
+        } else {
+            snprintf(tar_path, sizeof(tar_path), "%s", entry->d_name);
+        }
+
+        struct stat st;
+        if (stat(full_path, &st) != 0) {
+            printf("Warning: Cannot stat '%s', skipping\n", full_path);
+            continue;
+        }
+
+        if (S_ISDIR(st.st_mode)) {
+            // Recursively add subdirectory
+            if (add_directory_to_tar(tar, full_path, tar_path) != 0) {
+                closedir(dir);
+                return 1;
+            }
+        } else if (S_ISREG(st.st_mode)) {
+            // Add regular file
+            FILE* fp = fopen(full_path, "rb");
+            if (!fp) {
+                printf("Warning: Cannot open '%s', skipping\n", full_path);
+                continue;
+            }
+
+            // Get file size
+            fseek(fp, 0, SEEK_END);
+            size_t file_size = ftell(fp);
+            fseek(fp, 0, SEEK_SET);
+
+            // Read file data
+            unsigned char* file_data = malloc(file_size);
+            if (!file_data) {
+                printf("Error: Memory allocation failed for '%s'\n", full_path);
+                fclose(fp);
+                closedir(dir);
+                return 1;
+            }
+
+            size_t bytes_read = fread(file_data, 1, file_size, fp);
+            fclose(fp);
+
+            if (bytes_read != file_size) {
+                printf("Warning: Could not read entire file '%s', skipping\n", full_path);
+                free(file_data);
+                continue;
+            }
+
+            // Write to TAR
+            if (mtar_write_file_header(tar, tar_path, file_size) != MTAR_ESUCCESS) {
+                printf("Error: Failed to write TAR header for '%s'\n", tar_path);
+                free(file_data);
+                closedir(dir);
+                return 1;
+            }
+
+            if (mtar_write_data(tar, file_data, file_size) != MTAR_ESUCCESS) {
+                printf("Error: Failed to write TAR data for '%s'\n", tar_path);
+                free(file_data);
+                closedir(dir);
+                return 1;
+            }
+
+            free(file_data);
+        }
+    }
+
+    closedir(dir);
+    return 0;
+}
+
+// Create TAR archive from directory
+int create_tar_archive(const char* dir_path, const char* tar_output_path) {
+    mtar_t tar;
+    
+    if (mtar_open(&tar, tar_output_path, "w") != MTAR_ESUCCESS) {
+        printf("Error: Cannot create TAR file '%s'\n", tar_output_path);
+        return 1;
+    }
+
+    // Get directory name for relative paths
+    char dir_name[512];
+    const char* last_slash = strrchr(dir_path, '/');
+    if (last_slash) {
+        strncpy(dir_name, last_slash + 1, sizeof(dir_name) - 1);
+    } else {
+        strncpy(dir_name, dir_path, sizeof(dir_name) - 1);
+    }
+    dir_name[sizeof(dir_name) - 1] = '\0';
+
+    // Add directory contents to TAR
+    int result = add_directory_to_tar(&tar, dir_path, dir_name);
+
+    // Finalize and close TAR
+    mtar_finalize(&tar);
+    mtar_close(&tar);
+
+    return result;
+}
+
+// Extract TAR archive to directory
+int extract_tar_archive(const char* tar_path, const char* output_dir) {
+    mtar_t tar;
+    mtar_header_t header;
+
+    if (mtar_open(&tar, tar_path, "r") != MTAR_ESUCCESS) {
+        printf("Error: Cannot open TAR file '%s'\n", tar_path);
+        return 1;
+    }
+
+    // Create output directory if it doesn't exist
+    mkdir(output_dir, 0755);
+
+    // Extract each file
+    while (mtar_read_header(&tar, &header) == MTAR_ESUCCESS) {
+        char output_path[2048];
+        snprintf(output_path, sizeof(output_path), "%s/%s", output_dir, header.name);
+
+        // Create parent directories
+        char* last_slash = strrchr(output_path, '/');
+        if (last_slash) {
+            char parent_dir[2048];
+            strncpy(parent_dir, output_path, last_slash - output_path);
+            parent_dir[last_slash - output_path] = '\0';
+            
+            // Create directories recursively
+            char* p = parent_dir;
+            while (*p) {
+                if (*p == '/') {
+                    *p = '\0';
+                    mkdir(parent_dir, 0755);
+                    *p = '/';
+                }
+                p++;
+            }
+            mkdir(parent_dir, 0755);
+        }
+
+        // Extract file data
+        unsigned char* data = malloc(header.size);
+        if (!data) {
+            printf("Error: Memory allocation failed\n");
+            mtar_close(&tar);
+            return 1;
+        }
+
+        if (mtar_read_data(&tar, data, header.size) != MTAR_ESUCCESS) {
+            printf("Error: Failed to read data for '%s'\n", header.name);
+            free(data);
+            mtar_close(&tar);
+            return 1;
+        }
+
+        // Write to file
+        FILE* fp = fopen(output_path, "wb");
+        if (!fp) {
+            printf("Error: Cannot create file '%s'\n", output_path);
+            free(data);
+            mtar_close(&tar);
+            return 1;
+        }
+
+        fwrite(data, 1, header.size, fp);
+        fclose(fp);
+        free(data);
+
+        mtar_next(&tar);
+    }
+
+    mtar_close(&tar);
+    return 0;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//      COMPRESSION FUNCTIONS
+////////////////////////////////////////////////////////////////////////////////
+
+// Compress file with gzip (miniz)
+int compress_file_gzip(const char* input_path, const char* output_path) {
+    // Read input file
+    FILE* in = fopen(input_path, "rb");
+    if (!in) {
+        printf("Error: Cannot open input file '%s'\n", input_path);
+        return 1;
+    }
+
+    fseek(in, 0, SEEK_END);
+    size_t input_size = ftell(in);
+    fseek(in, 0, SEEK_SET);
+
+    unsigned char* input_data = malloc(input_size);
+    if (!input_data) {
+        printf("Error: Memory allocation failed\n");
+        fclose(in);
+        return 1;
+    }
+
+    size_t bytes_read = fread(input_data, 1, input_size, in);
+    fclose(in);
+
+    if (bytes_read != input_size) {
+        printf("Error: Failed to read input file\n");
+        free(input_data);
+        return 1;
+    }
+
+    // Compress with miniz
+    mz_ulong compressed_size = compressBound(input_size);
+    unsigned char* compressed_data = malloc(compressed_size);
+    if (!compressed_data) {
+        printf("Error: Memory allocation failed\n");
+        free(input_data);
+        return 1;
+    }
+
+    int result = compress2(compressed_data, &compressed_size,
+                          input_data, input_size,
+                          MZ_BEST_COMPRESSION);
+
+    free(input_data);
+
+    if (result != MZ_OK) {
+        printf("Error: Compression failed (error code: %d)\n", result);
+        free(compressed_data);
+        return 1;
+    }
+
+    // Write compressed data
+    FILE* out = fopen(output_path, "wb");
+    if (!out) {
+        printf("Error: Cannot create output file '%s'\n", output_path);
+        free(compressed_data);
+        return 1;
+    }
+
+    fwrite(compressed_data, 1, compressed_size, out);
+    fclose(out);
+    free(compressed_data);
+
+    return 0;
+}
+
+// Decompress gzip file (miniz)
+int decompress_file_gzip(const char* input_path, const char* output_path) {
+    // Read compressed file
+    FILE* in = fopen(input_path, "rb");
+    if (!in) {
+        printf("Error: Cannot open compressed file '%s'\n", input_path);
+        return 1;
+    }
+
+    fseek(in, 0, SEEK_END);
+    size_t compressed_size = ftell(in);
+    fseek(in, 0, SEEK_SET);
+
+    unsigned char* compressed_data = malloc(compressed_size);
+    if (!compressed_data) {
+        printf("Error: Memory allocation failed\n");
+        fclose(in);
+        return 1;
+    }
+
+    size_t bytes_read = fread(compressed_data, 1, compressed_size, in);
+    fclose(in);
+
+    if (bytes_read != compressed_size) {
+        printf("Error: Failed to read compressed file\n");
+        free(compressed_data);
+        return 1;
+    }
+
+    // Estimate decompressed size (try multiple times if needed)
+    mz_ulong output_size = compressed_size * 10;
+    unsigned char* output_data = NULL;
+    int result;
+
+    for (int attempt = 0; attempt < 3; attempt++) {
+        output_data = realloc(output_data, output_size);
+        if (!output_data) {
+            printf("Error: Memory allocation failed\n");
+            free(compressed_data);
+            return 1;
+        }
+
+        mz_ulong temp_size = output_size;
+        result = uncompress(output_data, &temp_size, compressed_data, compressed_size);
+
+        if (result == MZ_OK) {
+            output_size = temp_size;
+            break;
+        } else if (result == MZ_BUF_ERROR) {
+            // Buffer too small, try larger
+            output_size *= 2;
+        } else {
+            printf("Error: Decompression failed (error code: %d)\n", result);
+            free(compressed_data);
+            free(output_data);
+            return 1;
+        }
+    }
+
+    free(compressed_data);
+
+    if (result != MZ_OK) {
+        printf("Error: Decompression failed after multiple attempts\n");
+        free(output_data);
+        return 1;
+    }
+
+    // Write decompressed data
+    FILE* out = fopen(output_path, "wb");
+    if (!out) {
+        printf("Error: Cannot create output file '%s'\n", output_path);
+        free(output_data);
+        return 1;
+    }
+
+    fwrite(output_data, 1, output_size, out);
+    fclose(out);
+    free(output_data);
+
+    return 0;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//      HIGH-LEVEL DIRECTORY ENCRYPTION/DECRYPTION
+////////////////////////////////////////////////////////////////////////////////
+
+// Encrypt directory: TAR → GZIP → Encrypt
+int encrypt_directory(const char* dir_path, const char* pad_identifier, const char* output_file) {
+    char temp_tar[512];
+    char temp_gz[512];
+    int result = 0;
+
+    // Generate temporary file paths
+    snprintf(temp_tar, sizeof(temp_tar), "/tmp/otp_tar_%d.tar", getpid());
+    snprintf(temp_gz, sizeof(temp_gz), "/tmp/otp_gz_%d.tar.gz", getpid());
+
+    printf("Creating TAR archive...\n");
+    if (create_tar_archive(dir_path, temp_tar) != 0) {
+        printf("Error: Failed to create TAR archive\n");
+        return 1;
+    }
+
+    printf("Compressing archive...\n");
+    if (compress_file_gzip(temp_tar, temp_gz) != 0) {
+        printf("Error: Failed to compress archive\n");
+        unlink(temp_tar);
+        return 1;
+    }
+
+    printf("Encrypting compressed archive...\n");
+    result = encrypt_file(pad_identifier, temp_gz, output_file, 0);
+
+    // Cleanup temporary files
+    unlink(temp_tar);
+    unlink(temp_gz);
+
+    if (result == 0) {
+        printf("Directory encrypted successfully: %s\n", output_file);
+    }
+
+    return result;
+}
+
+// Detect if file is a compressed TAR archive
+int is_compressed_tar_archive(const char* file_path) {
+    FILE* fp = fopen(file_path, "rb");
+    if (!fp) {
+        return 0;
+    }
+
+    unsigned char magic[512];
+    size_t bytes_read = fread(magic, 1, sizeof(magic), fp);
+    fclose(fp);
+
+    if (bytes_read < 2) {
+        return 0;
+    }
+
+    // Check for GZIP magic bytes (0x1f 0x8b)
+    if (magic[0] == 0x1f && magic[1] == 0x8b) {
+        return 1;
+    }
+
+    // Check for TAR magic ("ustar" at offset 257)
+    if (bytes_read >= 262 && memcmp(magic + 257, "ustar", 5) == 0) {
+        return 1;
+    }
+
+    return 0;
+}
+
+// Decrypt and extract directory: Decrypt → GUNZIP → Extract TAR
+int decrypt_and_extract_directory(const char* encrypted_file, const char* output_dir) {
+    char temp_decrypted[512];
+    char temp_tar[512];
+    int result = 0;
+
+    // Generate temporary file paths
+    snprintf(temp_decrypted, sizeof(temp_decrypted), "/tmp/otp_decrypt_%d", getpid());
+    snprintf(temp_tar, sizeof(temp_tar), "/tmp/otp_tar_%d.tar", getpid());
+
+    printf("Decrypting file...\n");
+    if (decrypt_file(encrypted_file, temp_decrypted) != 0) {
+        printf("Error: Failed to decrypt file\n");
+        return 1;
+    }
+
+    // Check if it's compressed
+    FILE* fp = fopen(temp_decrypted, "rb");
+    if (!fp) {
+        printf("Error: Cannot open decrypted file\n");
+        unlink(temp_decrypted);
+        return 1;
+    }
+
+    unsigned char magic[2];
+    fread(magic, 1, 2, fp);
+    fclose(fp);
+
+    if (magic[0] == 0x1f && magic[1] == 0x8b) {
+        // GZIP compressed
+        printf("Decompressing archive...\n");
+        if (decompress_file_gzip(temp_decrypted, temp_tar) != 0) {
+            printf("Error: Failed to decompress archive\n");
+            unlink(temp_decrypted);
+            return 1;
+        }
+        unlink(temp_decrypted);
+    } else {
+        // Not compressed, assume it's already TAR
+        rename(temp_decrypted, temp_tar);
+    }
+
+    printf("Extracting archive...\n");
+    result = extract_tar_archive(temp_tar, output_dir);
+
+    // Cleanup
+    unlink(temp_tar);
+
+    if (result == 0) {
+        printf("Directory extracted successfully to: %s\n", output_dir);
+    }
+
+    return result;
+}

src/crypto.c

@@ -297,7 +297,6 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
     }
 
     char text_buffer[MAX_INPUT_SIZE];
-    char chksum_hex[MAX_HASH_LENGTH];
     uint64_t current_offset;
 
     char pad_path[MAX_HASH_LENGTH + 20];
@@ -327,12 +326,8 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
         }
     }
 
-    // Calculate XOR checksum of pad file
+    // Use pad_chksum directly - it's already the checksum from the filename
-    if (calculate_checksum(pad_path, chksum_hex) != 0) {
+    // No need to recalculate by reading the entire pad file
-        printf("Error: Cannot calculate pad checksum\n");
-        free(pad_chksum);
-        return 1;
-    }
 
     // Get input text - either from parameter or user input
     if (input_text != NULL) {
@@ -464,7 +459,7 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
 
     // Use universal ASCII armor generator
     char* ascii_output;
-    if (generate_ascii_armor(chksum_hex, current_offset, ciphertext, input_len, &ascii_output) != 0) {
+    if (generate_ascii_armor(pad_chksum, current_offset, ciphertext, input_len, &ascii_output) != 0) {
         printf("Error: Failed to generate ASCII armor\n");
         free(pad_data);
         free(ciphertext);
@@ -746,7 +741,6 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
         return 1;
     }
 
-    char chksum_hex[MAX_HASH_LENGTH];
     uint64_t current_offset;
 
     char pad_path[MAX_HASH_LENGTH + 20];
@@ -791,12 +785,8 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
         }
     }
 
-    // Calculate XOR checksum of pad file
+    // Use pad_chksum directly - it's already the checksum from the filename
-    if (calculate_checksum(pad_path, chksum_hex) != 0) {
+    // No need to recalculate by reading the entire pad file
-        printf("Error: Cannot calculate pad checksum\n");
-        free(pad_chksum);
-        return 1;
-    }
 
     // Check if we have enough pad space
     struct stat pad_stat;
@@ -927,7 +917,7 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
 
         // Use universal ASCII armor generator
         char* ascii_output;
-        if (generate_ascii_armor(chksum_hex, current_offset, encrypted_data, file_size, &ascii_output) != 0) {
+        if (generate_ascii_armor(pad_chksum, current_offset, encrypted_data, file_size, &ascii_output) != 0) {
             printf("Error: Failed to generate ASCII armor\n");
             fclose(output_fp);
             free(encrypted_data);
@@ -961,7 +951,7 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
         // Pad checksum: 32 bytes (binary)
         unsigned char pad_chksum_bin[32];
         for (int i = 0; i < 32; i++) {
-            sscanf(chksum_hex + i*2, "%2hhx", &pad_chksum_bin[i]);
+            sscanf(pad_chksum + i*2, "%2hhx", &pad_chksum_bin[i]);
         }
         fwrite(pad_chksum_bin, 1, 32, output_fp);
 

src/entropy.c

@@ -219,8 +219,22 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
     unsigned char buffer[64 * 1024]; // 64KB chunks
     unsigned char keystream[64 * 1024];
     uint64_t offset = 0;
-    uint32_t counter = 0;
+    uint32_t counter_low = 0;
+    uint32_t counter_high = 0;
     time_t start_time = time(NULL);
+    
+    // Use extended counter for pads larger than 256GB
+    // 256GB = 2^32 blocks * 64 bytes = 274,877,906,944 bytes
+    int use_extended = (pad_size > 274877906944ULL);
+    
+    // For extended mode, use reduced 8-byte nonce
+    unsigned char nonce_reduced[8];
+    if (use_extended) {
+        memcpy(nonce_reduced, nonce + 4, 8);
+        if (display_progress) {
+            printf("Using extended counter mode for large pad (>256GB)\n");
+        }
+    }
 
     while (offset < pad_size) {
         size_t chunk_size = sizeof(buffer);
@@ -237,7 +251,15 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
         }
 
         // Generate keystream for this chunk
-        if (chacha20_encrypt(key, counter, nonce, buffer, keystream, chunk_size) != 0) {
+        int chacha_result;
+        if (use_extended) {
+            chacha_result = chacha20_encrypt_extended(key, counter_low, counter_high,
+                                                      nonce_reduced, buffer, keystream, chunk_size);
+        } else {
+            chacha_result = chacha20_encrypt(key, counter_low, nonce, buffer, keystream, chunk_size);
+        }
+        
+        if (chacha_result != 0) {
             printf("Error: Chacha20 keystream generation failed\n");
             fclose(pad_file);
             chmod(pad_path, S_IRUSR);
@@ -265,7 +287,16 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
         }
 
         offset += chunk_size;
-        counter += (chunk_size + 63) / 64; // Round up for block count
+        
+        // Update counters
+        uint32_t blocks = (chunk_size + 63) / 64; // Round up for block count
+        uint32_t old_counter_low = counter_low;
+        counter_low += blocks;
+        
+        // Check for overflow and increment high counter
+        if (counter_low < old_counter_low) {
+            counter_high++;
+        }
 
         // Show progress for large pads
         if (display_progress && offset % (64 * 1024 * 1024) == 0) { // Every 64MB
@@ -282,7 +313,8 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
 
     if (display_progress) {
         show_progress(pad_size, pad_size, start_time);
-        printf("\n✓ Entropy successfully added to pad using Chacha20\n");
+        printf("\n✓ Entropy successfully added to pad using Chacha20%s\n",
+               use_extended ? " (extended counter)" : "");
         printf("✓ Pad integrity maintained\n");
         printf("✓ %zu bytes of entropy distributed across entire pad\n", entropy_size);
         printf("✓ Pad restored to read-only mode\n");

src/main.h

@@ -23,7 +23,7 @@
 #include <ctype.h>
 
 // Version - Updated automatically by build.sh
-#define OTP_VERSION "v0.3.34"
+#define OTP_VERSION "v0.3.42"
 
 // Constants
 #define MAX_INPUT_SIZE 4096
@@ -130,6 +130,7 @@ char* get_preferred_editor(void);
 char* get_preferred_file_manager(void);
 int launch_text_editor(const char* initial_content, char* result_buffer, size_t buffer_size);
 int launch_file_manager(const char* start_directory, char* selected_file, size_t buffer_size);
+int launch_directory_manager(const char* start_directory, char* selected_dir, size_t buffer_size);
 
 ////////////////////////////////////////////////////////////////////////////////
 //      CORE CRYPTOGRAPHIC OPERATIONS
@@ -238,6 +239,23 @@ int update_pad_checksum_after_entropy(const char* old_chksum, char* new_chksum);
 int rename_pad_files_safely(const char* old_chksum, const char* new_chksum);
 int is_pad_unused(const char* pad_chksum);
 
+////////////////////////////////////////////////////////////////////////////////
+//      DIRECTORY ARCHIVING AND COMPRESSION FUNCTIONS
+////////////////////////////////////////////////////////////////////////////////
+
+// Directory encryption/decryption (TAR + GZIP + OTP)
+int encrypt_directory(const char* dir_path, const char* pad_identifier, const char* output_file);
+int decrypt_and_extract_directory(const char* encrypted_file, const char* output_dir);
+int is_compressed_tar_archive(const char* file_path);
+
+// TAR archive operations
+int create_tar_archive(const char* dir_path, const char* tar_output_path);
+int extract_tar_archive(const char* tar_path, const char* output_dir);
+
+// Compression operations
+int compress_file_gzip(const char* input_path, const char* output_path);
+int decompress_file_gzip(const char* input_path, const char* output_path);
+
 ////////////////////////////////////////////////////////////////////////////////
 //      DIRECTORY MANAGEMENT FUNCTIONS
 ////////////////////////////////////////////////////////////////////////////////
@@ -314,6 +332,7 @@ int handle_decrypt_menu(void);
 int handle_pads_menu(void);
 int handle_text_encrypt(void);
 int handle_file_encrypt(void);
+int handle_directory_encrypt(void);
 int handle_verify_pad(const char* pad_chksum);
 int handle_delete_pad(const char* pad_chksum);
 

src/nostr_chacha20.c

@@ -129,8 +129,8 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
     return 0;
 }
 
-int chacha20_encrypt(const uint8_t key[32], uint32_t counter, 
+int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
-                     const uint8_t nonce[12], const uint8_t* input, 
+                     const uint8_t nonce[12], const uint8_t* input,
                      uint8_t* output, size_t length) {
     uint8_t keystream[CHACHA20_BLOCK_SIZE];
     size_t offset = 0;
@@ -161,3 +161,45 @@ int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
     
     return 0;
 }
+
+int chacha20_encrypt_extended(const uint8_t key[32], uint32_t counter_low,
+                               uint32_t counter_high, const uint8_t nonce[8],
+                               const uint8_t* input, uint8_t* output, size_t length) {
+    uint8_t keystream[CHACHA20_BLOCK_SIZE];
+    uint8_t extended_nonce[12];
+    size_t offset = 0;
+    
+    while (length > 0) {
+        /* Build extended 12-byte nonce: [counter_high (4 bytes)][nonce (8 bytes)] */
+        u32_to_bytes_le(counter_high, extended_nonce);
+        memcpy(extended_nonce + 4, nonce, 8);
+        
+        /* Generate keystream block using extended nonce */
+        int ret = chacha20_block(key, counter_low, extended_nonce, keystream);
+        if (ret != 0) {
+            return ret;
+        }
+        
+        /* XOR with input to produce output */
+        size_t block_len = (length < CHACHA20_BLOCK_SIZE) ? length : CHACHA20_BLOCK_SIZE;
+        for (size_t i = 0; i < block_len; i++) {
+            output[offset + i] = input[offset + i] ^ keystream[i];
+        }
+        
+        /* Move to next block */
+        offset += block_len;
+        length -= block_len;
+        counter_low++;
+        
+        /* Check for counter_low overflow and increment counter_high */
+        if (counter_low == 0) {
+            counter_high++;
+            /* Check for counter_high overflow (extremely unlikely - > 1 exabyte) */
+            if (counter_high == 0) {
+                return -1; /* Extended counter wrapped around */
+            }
+        }
+    }
+    
+    return 0;
+}

src/nostr_chacha20.h

@@ -63,10 +63,10 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
 
 /**
  * ChaCha20 encryption/decryption
- * 
+ *
  * Encrypts or decrypts data using ChaCha20 stream cipher.
  * Since ChaCha20 is a stream cipher, encryption and decryption are the same operation.
- * 
+ *
  * @param key[in]           32-byte key
  * @param counter[in]       Initial 32-bit counter value
  * @param nonce[in]         12-byte nonce
@@ -75,10 +75,29 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
  * @param length[in]        Length of input data in bytes
  * @return                  0 on success, negative on error
  */
-int chacha20_encrypt(const uint8_t key[32], uint32_t counter, 
+int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
-                     const uint8_t nonce[12], const uint8_t* input, 
+                     const uint8_t nonce[12], const uint8_t* input,
                      uint8_t* output, size_t length);
 
+/**
+ * ChaCha20 encryption/decryption with extended counter (64-bit)
+ *
+ * Extended version that supports files larger than 256GB by using
+ * part of the nonce as a high-order counter extension.
+ *
+ * @param key[in]           32-byte key
+ * @param counter_low[in]   Initial 32-bit counter value (low bits)
+ * @param counter_high[in]  Initial 32-bit counter value (high bits)
+ * @param nonce[in]         8-byte reduced nonce (instead of 12)
+ * @param input[in]         Input data to encrypt/decrypt
+ * @param output[out]       Output buffer (can be same as input)
+ * @param length[in]        Length of input data in bytes
+ * @return                  0 on success, negative on error
+ */
+int chacha20_encrypt_extended(const uint8_t key[32], uint32_t counter_low,
+                               uint32_t counter_high, const uint8_t nonce[8],
+                               const uint8_t* input, uint8_t* output, size_t length);
+
 /*
  * ============================================================================
  * UTILITY FUNCTIONS

src/pads.c

@@ -253,10 +253,10 @@ int generate_pad(uint64_t size_bytes, int display_progress) {
     }
 
     // Initialize state file with offset 32 (first 32 bytes reserved for checksum encryption)
-    FILE* state_file = fopen(state_path, "wb");
+    FILE* state_file = fopen(state_path, "w");
     if (state_file) {
         uint64_t reserved_bytes = 32;
-        fwrite(&reserved_bytes, sizeof(uint64_t), 1, state_file);
+        fprintf(state_file, "offset=%lu\n", reserved_bytes);
         fclose(state_file);
     } else {
         printf("Error: Failed to create state file\n");
@@ -292,7 +292,7 @@ int read_state_offset(const char* pad_chksum, uint64_t* offset) {
         return 0;
     }
 
-    // Try to read as text format first (new format)
+    // Read text format only (required format: "offset=<number>")
     char line[128];
     if (fgets(line, sizeof(line), state_file)) {
         // Check if it's text format (starts with "offset=")
@@ -302,21 +302,13 @@ int read_state_offset(const char* pad_chksum, uint64_t* offset) {
             return 0;
         }
         
-        // Not text format, try binary format (legacy)
+        // Not in proper text format - error
         fclose(state_file);
-        state_file = fopen(state_filename, "rb");
+        fprintf(stderr, "Error: State file '%s' is not in proper text format\n", state_filename);
-        if (!state_file) {
+        fprintf(stderr, "Expected format: offset=<number>\n");
-            *offset = 0;
+        fprintf(stderr, "Please convert old binary state files to text format\n");
-            return 0;
+        *offset = 0;
-        }
+        return 1;
-        
-        if (fread(offset, sizeof(uint64_t), 1, state_file) != 1) {
-            fclose(state_file);
-            *offset = 0;
-            return 0;
-        }
-        fclose(state_file);
-        return 0;
     }
 
     fclose(state_file);
@@ -478,6 +470,13 @@ char* select_pad_interactive(const char* title, const char* prompt, pad_filter_t
         return NULL;
     }
 
+    // If only one pad available, auto-select it
+    if (pad_count == 1) {
+        printf("\n%s\n", title);
+        printf("Only one pad available - auto-selecting: %.16s...\n\n", pads[0].chksum);
+        return strdup(pads[0].chksum);
+    }
+
     // Calculate minimal unique prefixes for each pad
     char prefixes[100][65];
     int prefix_lengths[100];

src/ui.c

@@ -99,6 +99,9 @@ int interactive_mode(void) {
             case 'F':
                 handle_file_encrypt();
                 break;
+            case 'R':
+                handle_directory_encrypt();
+                break;
             case 'D':
                 handle_decrypt_menu();
                 break;
@@ -125,11 +128,12 @@ void show_main_menu(void) {
     print_centered_header(header, 0);
     printf("\n");
 
-    printf(" \033[4mT\033[0mext encrypt\n");    //TEXT ENCRYPT
+    printf(" \033[4mT\033[0mext encrypt\n");       //TEXT ENCRYPT
-    printf(" \033[4mF\033[0mile encrypt\n");    //FILE ENCRYPT
+    printf(" \033[4mF\033[0mile encrypt\n");       //FILE ENCRYPT
-    printf(" \033[4mD\033[0mecrypt\n");         //DECRYPT
+    printf(" Di\033[4mr\033[0mectory encrypt\n");  //DIRECTORY ENCRYPT
-    printf(" \033[4mP\033[0mads\n");            //PADS
+    printf(" \033[4mD\033[0mecrypt\n");            //DECRYPT
-    printf(" E\033[4mx\033[0mit\n");            //EXIT
+    printf(" \033[4mP\033[0mads\n");               //PADS
+    printf(" E\033[4mx\033[0mit\n");               //EXIT
     printf("\nSelect option: ");
 }
 
@@ -352,7 +356,23 @@ int handle_decrypt_menu(void) {
             return 1;
         }
 
-        return decrypt_file(selected_file, output_file);
+        // Check if it's a directory archive
+        if (strstr(selected_file, ".tar.gz.otp") || strstr(selected_file, ".tar.otp")) {
+            // It's a directory archive - extract to directory
+            char extract_dir[512];
+            strncpy(extract_dir, output_file, sizeof(extract_dir) - 1);
+            extract_dir[sizeof(extract_dir) - 1] = '\0';
+            
+            // Remove .tar.gz.otp or .tar.otp extension to get directory name
+            char* ext = strstr(extract_dir, ".tar.gz.otp");
+            if (!ext) ext = strstr(extract_dir, ".tar.otp");
+            if (ext) *ext = '\0';
+            
+            printf("Extracting directory archive to: %s/\n", extract_dir);
+            return decrypt_and_extract_directory(selected_file, extract_dir);
+        } else {
+            return decrypt_file(selected_file, output_file);
+        }
     }
     else if (strncmp(input_line, "-----BEGIN OTP MESSAGE-----", 27) == 0) {
         // Looks like ASCII armor - collect the full message
@@ -404,7 +424,23 @@ int handle_decrypt_menu(void) {
                 return 1;
             }
 
-            return decrypt_file(input_line, output_file);
+            // Check if it's a directory archive
+            if (strstr(input_line, ".tar.gz.otp") || strstr(input_line, ".tar.otp")) {
+                // It's a directory archive - extract to directory
+                char extract_dir[512];
+                strncpy(extract_dir, output_file, sizeof(extract_dir) - 1);
+                extract_dir[sizeof(extract_dir) - 1] = '\0';
+                
+                // Remove .tar.gz.otp or .tar.otp extension to get directory name
+                char* ext = strstr(extract_dir, ".tar.gz.otp");
+                if (!ext) ext = strstr(extract_dir, ".tar.otp");
+                if (ext) *ext = '\0';
+                
+                printf("Extracting directory archive to: %s/\n", extract_dir);
+                return decrypt_and_extract_directory(input_line, extract_dir);
+            } else {
+                return decrypt_file(input_line, output_file);
+            }
         } else {
             printf("Input not recognized as ASCII armor or valid file path.\n");
             return 1;
@@ -501,5 +537,86 @@ int handle_file_encrypt(void) {
 
     int result = encrypt_file(selected_pad, input_file, output_filename, ascii_armor);
     free(selected_pad);
+    return result;
+}
+
+int handle_directory_encrypt(void) {
+    printf("\n");
+    print_centered_header("Directory Encrypt", 0);
+
+    // Directory selection options
+    printf("\nDirectory selection options:\n");
+    printf(" 1. Type directory path directly\n");
+    printf(" 2. Use file manager (navigate to directory)\n");
+    printf("Enter choice (1-2): ");
+
+    char choice_input[10];
+    char dir_path[512];
+
+    if (!fgets(choice_input, sizeof(choice_input), stdin)) {
+        printf("Error: Failed to read input\n");
+        return 1;
+    }
+
+    if (atoi(choice_input) == 2) {
+        // Use directory manager
+        if (launch_directory_manager(".", dir_path, sizeof(dir_path)) != 0) {
+            printf("Falling back to manual directory path entry.\n");
+            printf("Enter directory path to encrypt: ");
+            if (!fgets(dir_path, sizeof(dir_path), stdin)) {
+                printf("Error: Failed to read input\n");
+                return 1;
+            }
+            dir_path[strcspn(dir_path, "\n")] = 0;
+        }
+    } else {
+        // Direct directory path input
+        printf("Enter directory path to encrypt: ");
+        if (!fgets(dir_path, sizeof(dir_path), stdin)) {
+            printf("Error: Failed to read input\n");
+            return 1;
+        }
+        dir_path[strcspn(dir_path, "\n")] = 0;
+    }
+
+    // Check if directory exists
+    struct stat st;
+    if (stat(dir_path, &st) != 0 || !S_ISDIR(st.st_mode)) {
+        printf("Error: '%s' is not a valid directory\n", dir_path);
+        return 1;
+    }
+
+    // Select pad
+    char* selected_pad = select_pad_interactive("Select Pad for Directory Encryption",
+                                              "Select pad (by prefix)",
+                                              PAD_FILTER_ALL, 1);
+    if (!selected_pad) {
+        printf("Directory encryption cancelled.\n");
+        return 1;
+    }
+
+    // Generate default output filename
+    char default_output[1024];
+    const char* dir_name = strrchr(dir_path, '/');
+    if (dir_name) {
+        dir_name++; // Skip the '/'
+    } else {
+        dir_name = dir_path;
+    }
+    
+    snprintf(default_output, sizeof(default_output), "%s.tar.gz.otp", dir_name);
+
+    // Get output filename
+    char output_file[512];
+    if (get_filename_with_default("Output filename:", default_output, output_file, sizeof(output_file)) != 0) {
+        printf("Error: Failed to read input\n");
+        free(selected_pad);
+        return 1;
+    }
+
+    // Encrypt directory
+    int result = encrypt_directory(dir_path, selected_pad, output_file);
+    free(selected_pad);
+    
     return result;
 }

src/util.c

@@ -240,6 +240,83 @@ int launch_file_manager(const char* start_directory, char* selected_file, size_t
     return 1; // Fall back to manual entry
 }
 
+int launch_directory_manager(const char* start_directory, char* selected_dir, size_t buffer_size) {
+    char* fm = get_preferred_file_manager();
+    if (!fm) {
+        printf("No file manager found. Please install ranger, fzf, nnn, or lf.\n");
+        printf("Falling back to manual directory path entry.\n");
+        return 1; // Fall back to manual entry
+    }
+
+    char temp_filename[64];
+    snprintf(temp_filename, sizeof(temp_filename), "/tmp/otp_dir_%ld.tmp", time(NULL));
+
+    char command[512];
+    int result = 1;
+
+    printf("Opening %s for directory selection...\n", fm);
+    printf("Navigate INTO the directory you want to encrypt, then press 'q' to quit and select it.\n");
+
+    if (strcmp(fm, "ranger") == 0) {
+        snprintf(command, sizeof(command), "cd '%s' && ranger --choosedir=%s",
+                start_directory ? start_directory : ".", temp_filename);
+    } else if (strcmp(fm, "fzf") == 0) {
+        // fzf doesn't have directory-only mode easily, use find
+        snprintf(command, sizeof(command), "cd '%s' && find . -type d | fzf > %s",
+                start_directory ? start_directory : ".", temp_filename);
+    } else if (strcmp(fm, "nnn") == 0) {
+        snprintf(command, sizeof(command), "cd '%s' && nnn -p %s",
+                start_directory ? start_directory : ".", temp_filename);
+    } else if (strcmp(fm, "lf") == 0) {
+        snprintf(command, sizeof(command), "cd '%s' && lf -selection-path=%s",
+                start_directory ? start_directory : ".", temp_filename);
+    }
+
+    result = system(command);
+
+    if (result == 0 || result == 256) { // Some file managers return 256 on success
+        // Read selected directory from temp file
+        FILE* temp_file = fopen(temp_filename, "r");
+        if (temp_file) {
+            if (fgets(selected_dir, buffer_size, temp_file)) {
+                // Remove trailing newline
+                selected_dir[strcspn(selected_dir, "\n\r")] = 0;
+
+                // For relative paths, make absolute if needed
+                if (selected_dir[0] == '.' && selected_dir[1] == '/') {
+                    char current_dir[512];
+                    if (getcwd(current_dir, sizeof(current_dir))) {
+                        char abs_path[1024];
+                        snprintf(abs_path, sizeof(abs_path), "%s/%s", current_dir, selected_dir + 2);
+                        strncpy(selected_dir, abs_path, buffer_size - 1);
+                        selected_dir[buffer_size - 1] = '\0';
+                    }
+                } else if (selected_dir[0] != '/') {
+                    // Relative path without ./
+                    char current_dir[512];
+                    if (getcwd(current_dir, sizeof(current_dir))) {
+                        char abs_path[1024];
+                        snprintf(abs_path, sizeof(abs_path), "%s/%s", current_dir, selected_dir);
+                        strncpy(selected_dir, abs_path, buffer_size - 1);
+                        selected_dir[buffer_size - 1] = '\0';
+                    }
+                }
+
+                fclose(temp_file);
+                unlink(temp_filename);
+                free(fm);
+                return 0; // Success
+            }
+            fclose(temp_file);
+        }
+    }
+
+    // Clean up and indicate failure
+    unlink(temp_filename);
+    free(fm);
+    return 1; // Fall back to manual entry
+}
+
 // Stdin detection functions implementation
 int has_stdin_data(void) {
     // Check if stdin is a pipe/redirect (not a terminal)

tests/test_chacha20_extended.c

@@ -0,0 +1,263 @@
+/*
+ * test_chacha20_extended.c - Test ChaCha20 extended counter implementation
+ * 
+ * This test verifies that the extended counter properly handles:
+ * 1. Counter overflow at 2^32 blocks (256GB boundary)
+ * 2. Correct keystream generation across the overflow boundary
+ * 3. No duplicate keystream blocks
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include "../src/nostr_chacha20.h"
+
+#define TEST_BLOCK_SIZE 64
+#define BLOCKS_NEAR_OVERFLOW 10  // Test blocks around overflow point
+
+// Test helper: Compare two blocks for equality
+int blocks_equal(const uint8_t* block1, const uint8_t* block2, size_t len) {
+    return memcmp(block1, block2, len) == 0;
+}
+
+// Test 1: Verify extended counter handles overflow correctly
+int test_counter_overflow() {
+    printf("Test 1: Counter overflow handling\n");
+    printf("  Testing counter transition from 0xFFFFFFFF to 0x00000000...\n");
+    
+    uint8_t key[32];
+    uint8_t nonce[8];
+    uint8_t input[TEST_BLOCK_SIZE];
+    uint8_t output1[TEST_BLOCK_SIZE];
+    uint8_t output2[TEST_BLOCK_SIZE];
+    uint8_t output3[TEST_BLOCK_SIZE];
+    
+    // Initialize test data
+    memset(key, 0xAA, 32);
+    memset(nonce, 0xBB, 8);
+    memset(input, 0, TEST_BLOCK_SIZE);
+    
+    // Test at counter_low = 0xFFFFFFFE, counter_high = 0
+    uint32_t counter_low = 0xFFFFFFFE;
+    uint32_t counter_high = 0;
+    
+    printf("  Block at counter_low=0xFFFFFFFE, counter_high=0...\n");
+    if (chacha20_encrypt_extended(key, counter_low, counter_high, nonce, 
+                                   input, output1, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Error at counter_low=0xFFFFFFFE\n");
+        return 1;
+    }
+    
+    // Test at counter_low = 0xFFFFFFFF, counter_high = 0
+    counter_low = 0xFFFFFFFF;
+    printf("  Block at counter_low=0xFFFFFFFF, counter_high=0...\n");
+    if (chacha20_encrypt_extended(key, counter_low, counter_high, nonce, 
+                                   input, output2, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Error at counter_low=0xFFFFFFFF\n");
+        return 1;
+    }
+    
+    // Test at counter_low = 0x00000000, counter_high = 1 (after overflow)
+    counter_low = 0x00000000;
+    counter_high = 1;
+    printf("  Block at counter_low=0x00000000, counter_high=1...\n");
+    if (chacha20_encrypt_extended(key, counter_low, counter_high, nonce, 
+                                   input, output3, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Error at counter_low=0x00000000, counter_high=1\n");
+        return 1;
+    }
+    
+    // Verify all three blocks are different (no keystream reuse)
+    if (blocks_equal(output1, output2, TEST_BLOCK_SIZE)) {
+        printf("  ❌ FAILED: Blocks at 0xFFFFFFFE and 0xFFFFFFFF are identical!\n");
+        return 1;
+    }
+    
+    if (blocks_equal(output2, output3, TEST_BLOCK_SIZE)) {
+        printf("  ❌ FAILED: Blocks at 0xFFFFFFFF,0 and 0x00000000,1 are identical!\n");
+        return 1;
+    }
+    
+    if (blocks_equal(output1, output3, TEST_BLOCK_SIZE)) {
+        printf("  ❌ FAILED: Blocks at 0xFFFFFFFE,0 and 0x00000000,1 are identical!\n");
+        return 1;
+    }
+    
+    printf("  ✓ All blocks are unique across overflow boundary\n");
+    printf("  ✓ PASSED\n\n");
+    return 0;
+}
+
+// Test 2: Simulate processing data that crosses 256GB boundary
+int test_large_file_simulation() {
+    printf("Test 2: Large file simulation (256GB+ boundary)\n");
+    printf("  Simulating processing across 256GB boundary...\n");
+    
+    uint8_t key[32];
+    uint8_t nonce[8];
+    uint8_t input[1024];
+    uint8_t output[1024];
+    
+    // Initialize test data
+    memset(key, 0x55, 32);
+    memset(nonce, 0x77, 8);
+    for (int i = 0; i < 1024; i++) {
+        input[i] = i & 0xFF;
+    }
+    
+    // Simulate being at 256GB - 512 bytes (just before overflow)
+    // 256GB = 2^32 blocks * 64 bytes = 274,877,906,944 bytes
+    // Block number at 256GB - 512 bytes = 2^32 - 8 blocks
+    uint32_t counter_low = 0xFFFFFFF8;  // 2^32 - 8
+    uint32_t counter_high = 0;
+    
+    printf("  Processing 1KB starting at block 0xFFFFFFF8 (256GB - 512 bytes)...\n");
+    
+    // This should cross the overflow boundary
+    int result = chacha20_encrypt_extended(key, counter_low, counter_high, nonce, 
+                                           input, output, 1024);
+    
+    if (result != 0) {
+        printf("  ❌ FAILED: Error processing data across 256GB boundary\n");
+        return 1;
+    }
+    
+    printf("  ✓ Successfully processed data across 256GB boundary\n");
+    printf("  ✓ PASSED\n\n");
+    return 0;
+}
+
+// Test 3: Verify extended vs standard ChaCha20 compatibility
+int test_compatibility() {
+    printf("Test 3: Compatibility with standard ChaCha20\n");
+    printf("  Verifying extended mode matches standard mode when counter_high=0...\n");
+    
+    uint8_t key[32];
+    uint8_t nonce_standard[12];
+    uint8_t nonce_reduced[8];
+    uint8_t input[TEST_BLOCK_SIZE];
+    uint8_t output_standard[TEST_BLOCK_SIZE];
+    uint8_t output_extended[TEST_BLOCK_SIZE];
+    
+    // Initialize test data
+    memset(key, 0x33, 32);
+    memset(nonce_standard, 0x44, 12);
+    memcpy(nonce_reduced, nonce_standard + 4, 8);  // Extract last 8 bytes
+    memset(input, 0, TEST_BLOCK_SIZE);
+    
+    uint32_t counter = 42;
+    
+    // Standard ChaCha20
+    if (chacha20_encrypt(key, counter, nonce_standard, input, 
+                        output_standard, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Standard ChaCha20 error\n");
+        return 1;
+    }
+    
+    // Extended ChaCha20 with counter_high=0 and matching nonce
+    // The extended version builds nonce as [counter_high][nonce_reduced]
+    // So we need to ensure the first 4 bytes of nonce_standard are 0
+    uint8_t nonce_standard_zero[12] = {0};
+    memcpy(nonce_standard_zero + 4, nonce_reduced, 8);
+    
+    if (chacha20_encrypt(key, counter, nonce_standard_zero, input, 
+                        output_standard, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Standard ChaCha20 error\n");
+        return 1;
+    }
+    
+    if (chacha20_encrypt_extended(key, counter, 0, nonce_reduced, input, 
+                                  output_extended, TEST_BLOCK_SIZE) != 0) {
+        printf("  ❌ FAILED: Extended ChaCha20 error\n");
+        return 1;
+    }
+    
+    // Compare outputs
+    if (!blocks_equal(output_standard, output_extended, TEST_BLOCK_SIZE)) {
+        printf("  ❌ FAILED: Extended mode output differs from standard mode\n");
+        printf("  First 16 bytes of standard: ");
+        for (int i = 0; i < 16; i++) printf("%02x ", output_standard[i]);
+        printf("\n  First 16 bytes of extended: ");
+        for (int i = 0; i < 16; i++) printf("%02x ", output_extended[i]);
+        printf("\n");
+        return 1;
+    }
+    
+    printf("  ✓ Extended mode matches standard mode when counter_high=0\n");
+    printf("  ✓ PASSED\n\n");
+    return 0;
+}
+
+// Test 4: Stress test - verify no errors at extreme counter values
+int test_extreme_values() {
+    printf("Test 4: Extreme counter values\n");
+    printf("  Testing at various extreme counter positions...\n");
+    
+    uint8_t key[32];
+    uint8_t nonce[8];
+    uint8_t input[TEST_BLOCK_SIZE];
+    uint8_t output[TEST_BLOCK_SIZE];
+    
+    memset(key, 0x99, 32);
+    memset(nonce, 0x66, 8);
+    memset(input, 0, TEST_BLOCK_SIZE);
+    
+    // Test various extreme positions
+    struct {
+        uint32_t counter_low;
+        uint32_t counter_high;
+        const char* description;
+    } test_cases[] = {
+        {0x00000000, 0, "Start of first 256GB segment"},
+        {0xFFFFFFFF, 0, "End of first 256GB segment"},
+        {0x00000000, 1, "Start of second 256GB segment"},
+        {0xFFFFFFFF, 1, "End of second 256GB segment"},
+        {0x00000000, 0xFFFF, "Start of segment 65535"},
+        {0xFFFFFFFF, 0xFFFF, "End of segment 65535"},
+    };
+    
+    for (size_t i = 0; i < sizeof(test_cases) / sizeof(test_cases[0]); i++) {
+        printf("  Testing: %s (0x%08X, 0x%08X)...\n", 
+               test_cases[i].description,
+               test_cases[i].counter_low,
+               test_cases[i].counter_high);
+        
+        if (chacha20_encrypt_extended(key, test_cases[i].counter_low, 
+                                      test_cases[i].counter_high, nonce,
+                                      input, output, TEST_BLOCK_SIZE) != 0) {
+            printf("  ❌ FAILED at %s\n", test_cases[i].description);
+            return 1;
+        }
+    }
+    
+    printf("  ✓ All extreme values handled correctly\n");
+    printf("  ✓ PASSED\n\n");
+    return 0;
+}
+
+int main() {
+    printf("=================================================================\n");
+    printf("ChaCha20 Extended Counter Test Suite\n");
+    printf("=================================================================\n\n");
+    
+    int failures = 0;
+    
+    failures += test_counter_overflow();
+    failures += test_large_file_simulation();
+    failures += test_compatibility();
+    failures += test_extreme_values();
+    
+    printf("=================================================================\n");
+    if (failures == 0) {
+        printf("✓ ALL TESTS PASSED\n");
+        printf("=================================================================\n");
+        printf("\nThe extended counter implementation is working correctly.\n");
+        printf("It can now handle pads larger than 256GB without overflow errors.\n");
+        return 0;
+    } else {
+        printf("❌ %d TEST(S) FAILED\n", failures);
+        printf("=================================================================\n");
+        return 1;
+    }
+}