Version v0.2.11 - Automatic version increment

Makefile

@@ -1,7 +1,7 @@
 CC = gcc
 CFLAGS = -Wall -Wextra -std=c99
-LIBS = -lssl -lcrypto
-LIBS_STATIC = -static -lssl -lcrypto -ldl -lpthread
+LIBS = 
+LIBS_STATIC = -static
 TARGET = otp
 SOURCE = otp.c
 VERSION_SOURCE = src/version.c

README.md

@@ -1,4 +1,4 @@
-# OTP Cipher - One Time Pad Implementation
+r# OTP Cipher - One Time Pad Implementation
 
 A secure one-time pad (OTP) cipher implementation in C with automatic versioning system.
 
@@ -25,10 +25,11 @@ Current version can be viewed with: `./otp --help` or by running the interactive
 ### Prerequisites
 
 - GCC compiler
-- OpenSSL development libraries (`libssl-dev` on Ubuntu/Debian)
 - Git (for version tracking)
 - Make
 
+**Note: OpenSSL is no longer required! This implementation is now completely self-contained.**
+
 ### Build Commands
 
 Use the included build script for automatic versioning:
@@ -125,10 +126,11 @@ These files are excluded from git (.gitignore) and regenerated on each build.
 ## Security Features
 
 - Uses `/dev/urandom` for cryptographically secure random number generation
-- Optional keyboard entropy mixing using HKDF (Hash-based Key Derivation Function)
-- SHA-256 pad integrity verification
+- Optional keyboard entropy mixing using simple XOR operations
+- Custom 256-bit XOR checksum for pad identification (encrypted with pad data)
 - Read-only pad files to prevent accidental modification
 - State tracking to prevent pad reuse
+- **Zero external crypto dependencies** - completely self-contained implementation
 
 ## File Structure
 

build.sh

@@ -50,6 +50,20 @@ increment_version() {
     print_status "Current version: $LATEST_TAG"
     print_status "New version: $NEW_VERSION"
     
+    # Stage all changes
+    if git add . 2>/dev/null; then
+        print_success "Staged all changes"
+    else
+        print_warning "Failed to stage changes (maybe not a git repository)"
+    fi
+    
+    # Commit changes with version message
+    if git commit -m "Version $NEW_VERSION - Automatic version increment" 2>/dev/null; then
+        print_success "Committed changes for version $NEW_VERSION"
+    else
+        print_warning "Failed to commit changes (maybe no changes to commit or not a git repository)"
+    fi
+    
     # Create new git tag
     if git tag "$NEW_VERSION" 2>/dev/null; then
         print_success "Created new version tag: $NEW_VERSION"

otp.c

@@ -12,14 +12,29 @@
 #include <ctype.h>
 #include <termios.h>
 #include <fcntl.h>
-#include <openssl/sha.h>
-#include <openssl/evp.h>
-#include <openssl/bio.h>
-#include <openssl/buffer.h>
-#include <openssl/kdf.h>
-#include <openssl/hmac.h>
 #include "src/version.h"
 
+// Custom base64 character set
+static const char base64_chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+static const int base64_decode_table[256] = {
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,62,-1,-1,-1,63,
+    52,53,54,55,56,57,58,59,60,61,-1,-1,-1,-2,-1,-1,
+    -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,
+    15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1,
+    -1,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,
+    41,42,43,44,45,46,47,48,49,50,51,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
+    -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
+};
+
 #define MAX_INPUT_SIZE 4096
 #define MAX_LINE_LENGTH 1024
 #define MAX_HASH_LENGTH 65
@@ -42,28 +57,28 @@ int decrypt_text(const char* pad_identifier);
 int setup_raw_terminal(struct termios* original_termios);
 void restore_terminal(struct termios* original_termios);
 int collect_keyboard_entropy(unsigned char* entropy_buffer, size_t max_size, size_t* collected);
-int hkdf_expand(const unsigned char* prk, size_t prk_len, 
-                const unsigned char* info, size_t info_len,
-                unsigned char* okm, size_t okm_len);
+void simple_entropy_mix(unsigned char* urandom_buffer, size_t buffer_size, 
+                         const unsigned char* entropy_data, size_t entropy_size);
 
 // Directory management
 int ensure_pads_directory(void);
-void get_pad_path(const char* hash, char* pad_path, char* state_path);
+void get_pad_path(const char* chksum, char* pad_path, char* state_path);
 
 // Utility functions
 uint64_t parse_size_string(const char* size_str);
 char* find_pad_by_prefix(const char* prefix);
 int list_available_pads(void);
-int show_pad_info(const char* hash);
+int show_pad_info(const char* chksum);
 int get_user_choice(int min, int max);
 void show_progress(uint64_t current, uint64_t total, time_t start_time);
 
 // File operations
-int read_state_offset(const char* pad_hash, uint64_t* offset);
-int write_state_offset(const char* pad_hash, uint64_t offset);
-int calculate_sha256(const char* filename, char* hash_hex);
-char* base64_encode(const unsigned char* input, int length);
-unsigned char* base64_decode(const char* input, int* output_length);
+int read_state_offset(const char* pad_chksum, uint64_t* offset);
+int write_state_offset(const char* pad_chksum, uint64_t offset);
+int calculate_checksum(const char* filename, char* checksum_hex);
+void xor_checksum_256(const unsigned char* data, size_t len, unsigned char checksum[32]);
+char* custom_base64_encode(const unsigned char* input, int length);
+unsigned char* custom_base64_decode(const char* input, int* output_length);
 
 // Menu functions
 void show_main_menu(void);
@@ -86,37 +101,46 @@ int interactive_mode(void) {
     
     while (1) {
         show_main_menu();
-        int choice = get_user_choice(1, 6);
+        char input[10];
+        if (fgets(input, sizeof(input), stdin)) {
+            char choice = toupper(input[0]);
             
             switch (choice) {
-            case 1:
+                case 'G':
                     handle_generate_menu();
                     break;
-            case 2:
+                case 'E':
                     handle_encrypt_menu();
                     break;
-            case 3:
+                case 'D':
                     handle_decrypt_menu();
                     break;
-            case 4:
+                case 'L':
                     list_available_pads();
                     break;
-            case 5: {
-                printf("Enter pad hash (or prefix): ");
+                case 'S': {
+                    printf("Enter pad checksum (or prefix): ");
                     char input[MAX_HASH_LENGTH];
                     if (fgets(input, sizeof(input), stdin)) {
                         input[strcspn(input, "\n")] = 0;
-                    char* hash = find_pad_by_prefix(input);
-                    if (hash) {
-                        show_pad_info(hash);
-                        free(hash);
+                        char* chksum = find_pad_by_prefix(input);
+                        if (chksum) {
+                            show_pad_info(chksum);
+                            free(chksum);
                         }
                     }
                     break;
                 }
-            case 6:
+                case 'X':
                     printf("Goodbye!\n");
                     return 0;
+                default:
+                    printf("Invalid option. Please select G, E, D, L, S, or X.\n");
+                    continue;
+            }
+        } else {
+            printf("Error reading input. Please try again.\n");
+            continue;
         }
         printf("\n");
     }
@@ -138,14 +162,14 @@ int command_line_mode(int argc, char* argv[]) {
     }
     else if (strcmp(argv[1], "encrypt") == 0) {
         if (argc != 3) {
-            printf("Usage: %s encrypt <pad_hash_or_prefix>\n", argv[0]);
+            printf("Usage: %s encrypt <pad_chksum_or_prefix>\n", argv[0]);
             return 1;
         }
         return encrypt_text(argv[2]);
     }
     else if (strcmp(argv[1], "decrypt") == 0) {
         if (argc != 3) {
-            printf("Usage: %s decrypt <pad_hash_or_prefix>\n", argv[0]);
+            printf("Usage: %s decrypt <pad_chksum_or_prefix>\n", argv[0]);
             return 1;
         }
         return decrypt_text(argv[2]);
@@ -161,13 +185,13 @@ int command_line_mode(int argc, char* argv[]) {
 
 void show_main_menu(void) {
     printf("=== Main Menu ===\n");
-    printf("1. Generate new pad\n");
-    printf("2. Encrypt message\n");
-    printf("3. Decrypt message\n");
-    printf("4. List available pads\n");
-    printf("5. Show pad information\n");
-    printf("6. Exit\n");
-    printf("\nSelect option (1-6): ");
+    printf("\033[4mG\033[0menerate new pad\n");
+    printf("\033[4mE\033[0mncrypt message\n");
+    printf("\033[4mD\033[0mecrypt message\n");
+    printf("\033[4mL\033[0mist available pads\n");
+    printf("\033[4mS\033[0mhow pad information\n");
+    printf("E\033[4mx\033[0mit\n");
+    printf("\nSelect option: ");
 }
 
 int handle_generate_menu(void) {
@@ -218,7 +242,7 @@ int handle_encrypt_menu(void) {
         return 1;
     }
     
-    printf("\nEnter pad selection (number, hash, or prefix): ");
+    printf("\nEnter pad selection (number, chksum, or prefix): ");
     char input[MAX_HASH_LENGTH];
     if (!fgets(input, sizeof(input), stdin)) {
         printf("Error: Failed to read input\n");
@@ -231,7 +255,7 @@ int handle_encrypt_menu(void) {
 
 int handle_decrypt_menu(void) {
     printf("\n=== Decrypt Message ===\n");
-    return decrypt_text(NULL);  // No pad selection needed - hash comes from message
+    return decrypt_text(NULL);  // No pad selection needed - chksum comes from message
 }
 
 uint64_t parse_size_string(const char* size_str) {
@@ -292,7 +316,7 @@ char* find_pad_by_prefix(const char* prefix) {
         int current = 0;
         rewinddir(dir);
         while ((entry = readdir(dir)) != NULL && match_count == 0) {
-            if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) { // 64 char hash + ".pad"
+            if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) { // 64 char chksum + ".pad"
                 current++;
                 if (current == selection) {
                     matches[match_count] = malloc(65);
@@ -353,15 +377,15 @@ int list_available_pads(void) {
     int count = 0;
     
     printf("Available pads:\n");
-    printf("%-4s %-20s %-12s %-12s %-8s\n", "No.", "Hash (first 16 chars)", "Size", "Used", "% Used");
+    printf("%-4s %-20s %-12s %-12s %-8s\n", "No.", "ChkSum (first 16 chars)", "Size", "Used", "% Used");
     printf("%-4s %-20s %-12s %-12s %-8s\n", "---", "-------------------", "----------", "----------", "------");
     
     while ((entry = readdir(dir)) != NULL) {
         if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
             count++;
-            char hash[65];
-            strncpy(hash, entry->d_name, 64);
-            hash[64] = '\0';
+            char chksum[65];
+            strncpy(chksum, entry->d_name, 64);
+            chksum[64] = '\0';
             
             // Get pad file size
             char full_path[300]; // Increased buffer size to accommodate longer paths
@@ -370,7 +394,7 @@ int list_available_pads(void) {
             if (stat(full_path, &st) == 0) {
                 // Get used bytes from state
                 uint64_t used_bytes;
-                read_state_offset(hash, &used_bytes);
+                read_state_offset(chksum, &used_bytes);
                 
                 // Format sizes
                 char size_str[32], used_str[32];
@@ -400,7 +424,7 @@ int list_available_pads(void) {
                 // Calculate percentage
                 double percentage = (double)used_bytes / st.st_size * 100.0;
                 
-                printf("%-4d %-20.16s %-12s %-12s %.1f%%\n", count, hash, size_str, used_str, percentage);
+                printf("%-4d %-20.16s %-12s %-12s %.1f%%\n", count, chksum, size_str, used_str, percentage);
             }
         }
     }
@@ -414,24 +438,24 @@ int list_available_pads(void) {
     return count;
 }
 
-int show_pad_info(const char* hash) {
+int show_pad_info(const char* chksum) {
     char pad_filename[MAX_HASH_LENGTH + 10];
     char state_filename[MAX_HASH_LENGTH + 10];
     
-    snprintf(pad_filename, sizeof(pad_filename), "%s.pad", hash);
-    snprintf(state_filename, sizeof(state_filename), "%s.state", hash);
+    snprintf(pad_filename, sizeof(pad_filename), "%s.pad", chksum);
+    snprintf(state_filename, sizeof(state_filename), "%s.state", chksum);
     
     struct stat st;
     if (stat(pad_filename, &st) != 0) {
-        printf("Pad not found: %s\n", hash);
+        printf("Pad not found: %s\n", chksum);
         return 1;
     }
     
     uint64_t used_bytes;
-    read_state_offset(hash, &used_bytes);
+    read_state_offset(chksum, &used_bytes);
     
     printf("=== Pad Information ===\n");
-    printf("Hash: %s\n", hash);
+    printf("ChkSum: %s\n", chksum);
     printf("File: %s\n", pad_filename);
     
     double size_gb = (double)st.st_size / (1024.0 * 1024.0 * 1024.0);
@@ -481,7 +505,7 @@ int generate_pad(uint64_t size_bytes, int display_progress) {
     char temp_filename[32];
     char pad_filename[MAX_HASH_LENGTH + 10];
     char state_filename[MAX_HASH_LENGTH + 10];
-    char hash_hex[MAX_HASH_LENGTH];
+    char chksum_hex[MAX_HASH_LENGTH];
     
     // Create temporary filename
     snprintf(temp_filename, sizeof(temp_filename), "temp_%ld.pad", time(NULL));
@@ -544,19 +568,19 @@ int generate_pad(uint64_t size_bytes, int display_progress) {
     fclose(urandom);
     fclose(pad_file);
     
-    // Calculate SHA-256 of the pad file
-    if (calculate_sha256(temp_filename, hash_hex) != 0) {
-        printf("Error: Cannot calculate pad hash\n");
+    // Calculate XOR checksum of the pad file
+    if (calculate_checksum(temp_filename, chksum_hex) != 0) {
+        printf("Error: Cannot calculate pad checksum\n");
         unlink(temp_filename);
         return 1;
     }
     
-    // Rename file to its hash
-    snprintf(pad_filename, sizeof(pad_filename), "%s.pad", hash_hex);
-    snprintf(state_filename, sizeof(state_filename), "%s.state", hash_hex);
+    // Rename file to its chksum
+    snprintf(pad_filename, sizeof(pad_filename), "%s.pad", chksum_hex);
+    snprintf(state_filename, sizeof(state_filename), "%s.state", chksum_hex);
     
     if (rename(temp_filename, pad_filename) != 0) {
-        printf("Error: Cannot rename pad file to hash-based name\n");
+        printf("Error: Cannot rename pad file to chksum-based name\n");
         unlink(temp_filename);
         return 1;
     }
@@ -567,7 +591,7 @@ int generate_pad(uint64_t size_bytes, int display_progress) {
     }
     
     // Initialize state file with offset 0
-    if (write_state_offset(hash_hex, 0) != 0) {
+    if (write_state_offset(chksum_hex, 0) != 0) {
         printf("Error: Failed to create state file\n");
         unlink(pad_filename);
         return 1;
@@ -575,7 +599,7 @@ int generate_pad(uint64_t size_bytes, int display_progress) {
     
     double size_gb = (double)size_bytes / (1024.0 * 1024.0 * 1024.0);
     printf("Generated pad: %s (%.2f GB)\n", pad_filename, size_gb);
-    printf("Pad hash: %s\n", hash_hex);
+    printf("Pad chksum: %s\n", chksum_hex);
     printf("State file: %s\n", state_filename);
     printf("Pad file set to read-only\n");
     
@@ -591,7 +615,7 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
     char temp_filename[64];
     char pad_path[MAX_HASH_LENGTH + 20];
     char state_path[MAX_HASH_LENGTH + 20];
-    char hash_hex[MAX_HASH_LENGTH];
+    char chksum_hex[MAX_HASH_LENGTH];
     
     // Create temporary filename
     snprintf(temp_filename, sizeof(temp_filename), "temp_%ld.pad", time(NULL));
@@ -671,35 +695,12 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
                                    MAX_ENTROPY_BUFFER - entropy_collected, &chunk_entropy);
             entropy_collected += chunk_entropy;
             
-            if (entropy_collected > 1024) { // Have enough entropy to mix
-                // Create HKDF PRK (extract phase)
-                unsigned char prk[32];
-                EVP_MD_CTX* hmac_ctx = EVP_MD_CTX_new();
-                EVP_PKEY* hmac_key = EVP_PKEY_new_raw_private_key(EVP_PKEY_HMAC, NULL, 
-                                                                  entropy_buffer, entropy_collected);
-                
-                if (hmac_ctx && hmac_key) {
-                    EVP_DigestSignInit(hmac_ctx, NULL, EVP_sha256(), NULL, hmac_key);
-                    EVP_DigestSignUpdate(hmac_ctx, urandom_buffer, chunk_size);
-                    size_t prk_len = sizeof(prk);
-                    EVP_DigestSignFinal(hmac_ctx, prk, &prk_len);
-                    
-                    // HKDF Expand phase
-                    const char* info = "OTP-PAD-CHUNK";
-                    if (hkdf_expand(prk, prk_len, (const unsigned char*)info, strlen(info),
-                                   output_buffer, chunk_size) == 0) {
-                        // Successfully mixed entropy
-                    } else {
-                        // Fallback to urandom only
+            if (entropy_collected > 512) { // Have enough entropy to mix
+                // Copy urandom data to output buffer
                 memcpy(output_buffer, urandom_buffer, chunk_size);
-                    }
                 
-                    EVP_PKEY_free(hmac_key);
-                    EVP_MD_CTX_free(hmac_ctx);
-                } else {
-                    // Fallback to urandom only
-                    memcpy(output_buffer, urandom_buffer, chunk_size);
-                }
+                // Simple XOR mixing with keyboard entropy
+                simple_entropy_mix(output_buffer, chunk_size, entropy_buffer, entropy_collected);
                 
                 // Reset entropy buffer for next chunk
                 entropy_collected = 0;
@@ -751,15 +752,15 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
     fclose(urandom);
     fclose(pad_file);
     
-    // Calculate SHA-256 of the pad file
-    if (calculate_sha256(temp_filename, hash_hex) != 0) {
-        printf("Error: Cannot calculate pad hash\n");
+    // Calculate XOR checksum of the pad file
+    if (calculate_checksum(temp_filename, chksum_hex) != 0) {
+        printf("Error: Cannot calculate pad checksum\n");
         unlink(temp_filename);
         return 1;
     }
     
     // Get final paths in pads directory
-    get_pad_path(hash_hex, pad_path, state_path);
+    get_pad_path(chksum_hex, pad_path, state_path);
     
     if (rename(temp_filename, pad_path) != 0) {
         printf("Error: Cannot move pad file to pads directory\n");
@@ -772,11 +773,11 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
         printf("Warning: Cannot set pad file to read-only\n");
     }
     
-    // Initialize state file with offset 0
+    // Initialize state file with offset 32 (first 32 bytes used for checksum encryption)
     FILE* state_file = fopen(state_path, "wb");
     if (state_file) {
-        uint64_t zero = 0;
-        fwrite(&zero, sizeof(uint64_t), 1, state_file);
+        uint64_t reserved_bytes = 32;
+        fwrite(&reserved_bytes, sizeof(uint64_t), 1, state_file);
         fclose(state_file);
     } else {
         printf("Error: Failed to create state file\n");
@@ -786,7 +787,7 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
     
     double size_gb = (double)size_bytes / (1024.0 * 1024.0 * 1024.0);
     printf("Generated pad: %s (%.2f GB)\n", pad_path, size_gb);
-    printf("Pad hash: %s\n", hash_hex);
+    printf("Pad checksum: %s\n", chksum_hex);
     printf("State file: %s\n", state_path);
     if (use_keyboard_entropy) {
         printf("Enhanced with keyboard entropy!\n");
@@ -797,37 +798,46 @@ int generate_pad_with_entropy(uint64_t size_bytes, int display_progress, int use
 }
 
 int encrypt_text(const char* pad_identifier) {
-    char* pad_hash = find_pad_by_prefix(pad_identifier);
-    if (!pad_hash) {
+    char* pad_chksum = find_pad_by_prefix(pad_identifier);
+    if (!pad_chksum) {
         return 1;
     }
     
     char input_text[MAX_INPUT_SIZE];
-    char hash_hex[MAX_HASH_LENGTH];
+    char chksum_hex[MAX_HASH_LENGTH];
     uint64_t current_offset;
     
     char pad_path[MAX_HASH_LENGTH + 20];
     char state_path[MAX_HASH_LENGTH + 20];
-    get_pad_path(pad_hash, pad_path, state_path);
+    get_pad_path(pad_chksum, pad_path, state_path);
     
     // Check if pad file exists
     if (access(pad_path, R_OK) != 0) {
         printf("Error: Pad file %s not found\n", pad_path);
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
     // Read current offset
-    if (read_state_offset(pad_hash, &current_offset) != 0) {
+    if (read_state_offset(pad_chksum, &current_offset) != 0) {
         printf("Error: Cannot read state file\n");
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
-    // Calculate SHA-256 of pad file
-    if (calculate_sha256(pad_path, hash_hex) != 0) {
-        printf("Error: Cannot calculate pad hash\n");
-        free(pad_hash);
+    // Ensure we never encrypt before offset 32 (reserved for checksum encryption)
+    if (current_offset < 32) {
+        printf("Warning: State offset below reserved area, adjusting to 32\n");
+        current_offset = 32;
+        if (write_state_offset(pad_chksum, current_offset) != 0) {
+            printf("Warning: Failed to update state file\n");
+        }
+    }
+    
+    // Calculate XOR checksum of pad file
+    if (calculate_checksum(pad_path, chksum_hex) != 0) {
+        printf("Error: Cannot calculate pad checksum\n");
+        free(pad_chksum);
         return 1;
     }
     
@@ -837,7 +847,7 @@ int encrypt_text(const char* pad_identifier) {
     
     if (fgets(input_text, sizeof(input_text), stdin) == NULL) {
         printf("Error: Failed to read input\n");
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
@@ -850,7 +860,7 @@ int encrypt_text(const char* pad_identifier) {
     
     if (input_len == 0) {
         printf("Error: No input provided\n");
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
@@ -858,7 +868,7 @@ int encrypt_text(const char* pad_identifier) {
     struct stat pad_stat;
     if (stat(pad_path, &pad_stat) != 0) {
         printf("Error: Cannot get pad file size\n");
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
@@ -866,7 +876,7 @@ int encrypt_text(const char* pad_identifier) {
         printf("Error: Not enough pad space remaining\n");
         printf("Need: %lu bytes, Available: %lu bytes\n", 
                input_len, (uint64_t)pad_stat.st_size - current_offset);
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
@@ -874,14 +884,14 @@ int encrypt_text(const char* pad_identifier) {
     FILE* pad_file = fopen(pad_path, "rb");
     if (!pad_file) {
         printf("Error: Cannot open pad file\n");
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
     if (fseek(pad_file, current_offset, SEEK_SET) != 0) {
         printf("Error: Cannot seek to offset in pad file\n");
         fclose(pad_file);
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     
@@ -890,7 +900,7 @@ int encrypt_text(const char* pad_identifier) {
         printf("Error: Cannot read pad data\n");
         free(pad_data);
         fclose(pad_file);
-        free(pad_hash);
+        free(pad_chksum);
         return 1;
     }
     fclose(pad_file);
@@ -902,17 +912,17 @@ int encrypt_text(const char* pad_identifier) {
     }
     
     // Encode as base64
-    char* base64_cipher = base64_encode(ciphertext, input_len);
+    char* base64_cipher = custom_base64_encode(ciphertext, input_len);
     
     // Update state offset
-    if (write_state_offset(pad_hash, current_offset + input_len) != 0) {
+    if (write_state_offset(pad_chksum, current_offset + input_len) != 0) {
         printf("Warning: Failed to update state file\n");
     }
     
     // Output in ASCII armor format
-    printf("\n-----BEGIN OTP MESSAGE-----\n");
+    printf("\n\n-----BEGIN OTP MESSAGE-----\n");
     printf("Version: %s\n", get_version());
-    printf("Pad-Hash: %s\n", hash_hex);
+    printf("Pad-ChkSum: %s\n", chksum_hex);
     printf("Pad-Offset: %lu\n", current_offset);
     printf("\n");
     
@@ -922,24 +932,24 @@ int encrypt_text(const char* pad_identifier) {
         printf("%.64s\n", base64_cipher + i);
     }
     
-    printf("-----END OTP MESSAGE-----\n\n");
+    printf("-----END OTP MESSAGE-----\n\n\n");
     
     // Cleanup
     free(pad_data);
     free(ciphertext);
     free(base64_cipher);
-    free(pad_hash);
+    free(pad_chksum);
     
     return 0;
 }
 
 int decrypt_text(const char* pad_identifier) {
-    // For command line mode, pad_identifier is ignored - we'll get the hash from the message
+    // For command line mode, pad_identifier is ignored - we'll get the chksum from the message
     (void)pad_identifier; // Suppress unused parameter warning
     
     char line[MAX_LINE_LENGTH];
-    char stored_hash[MAX_HASH_LENGTH];
-    char current_hash[MAX_HASH_LENGTH];
+    char stored_chksum[MAX_HASH_LENGTH];
+    char current_chksum[MAX_HASH_LENGTH];
     uint64_t pad_offset;
     char base64_data[MAX_INPUT_SIZE * 2] = {0};
     int in_data_section = 0;
@@ -962,9 +972,9 @@ int decrypt_text(const char* pad_identifier) {
         
         if (!found_begin) continue;
         
-        if (strncmp(line, "Pad-Hash: ", 10) == 0) {
-            strncpy(stored_hash, line + 10, 64);
-            stored_hash[64] = '\0';
+        if (strncmp(line, "Pad-ChkSum: ", 12) == 0) {
+            strncpy(stored_chksum, line + 12, 64);
+            stored_chksum[64] = '\0';
         }
         else if (strncmp(line, "Pad-Offset: ", 12) == 0) {
             pad_offset = strtoull(line + 12, NULL, 10);
@@ -982,29 +992,29 @@ int decrypt_text(const char* pad_identifier) {
         return 1;
     }
     
-    // Now we have the pad hash from the message, construct filename
+    // Now we have the pad chksum from the message, construct filename
     char pad_path[MAX_HASH_LENGTH + 20];
     char state_path[MAX_HASH_LENGTH + 20];
-    get_pad_path(stored_hash, pad_path, state_path);
+    get_pad_path(stored_chksum, pad_path, state_path);
     
     // Check if we have this pad
     if (access(pad_path, R_OK) != 0) {
-        printf("Error: Required pad not found: %s\n", stored_hash);
+        printf("Error: Required pad not found: %s\n", stored_chksum);
         printf("Available pads:\n");
         list_available_pads();
         return 1;
     }
     
     // Verify pad integrity
-    if (calculate_sha256(pad_path, current_hash) != 0) {
-        printf("Error: Cannot calculate current pad hash\n");
+    if (calculate_checksum(pad_path, current_chksum) != 0) {
+        printf("Error: Cannot calculate current pad checksum\n");
         return 1;
     }
     
-    if (strcmp(stored_hash, current_hash) != 0) {
+    if (strcmp(stored_chksum, current_chksum) != 0) {
         printf("Warning: Pad integrity check failed!\n");
-        printf("Expected: %s\n", stored_hash);
-        printf("Current:  %s\n", current_hash);
+        printf("Expected: %s\n", stored_chksum);
+        printf("Current:  %s\n", current_chksum);
         printf("Continue anyway? (y/N): ");
         fflush(stdout);
         
@@ -1020,7 +1030,7 @@ int decrypt_text(const char* pad_identifier) {
     
     // Decode base64
     int ciphertext_len;
-    unsigned char* ciphertext = base64_decode(base64_data, &ciphertext_len);
+    unsigned char* ciphertext = custom_base64_decode(base64_data, &ciphertext_len);
     if (!ciphertext) {
         printf("Error: Invalid base64 data\n");
         return 1;
@@ -1068,9 +1078,9 @@ int decrypt_text(const char* pad_identifier) {
     return 0;
 }
 
-int read_state_offset(const char* pad_hash, uint64_t* offset) {
+int read_state_offset(const char* pad_chksum, uint64_t* offset) {
     char state_filename[MAX_HASH_LENGTH + 20];
-    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", PADS_DIR, pad_hash);
+    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", PADS_DIR, pad_chksum);
     
     FILE* state_file = fopen(state_filename, "rb");
     if (!state_file) {
@@ -1088,9 +1098,9 @@ int read_state_offset(const char* pad_hash, uint64_t* offset) {
     return 0;
 }
 
-int write_state_offset(const char* pad_hash, uint64_t offset) {
+int write_state_offset(const char* pad_chksum, uint64_t offset) {
     char state_filename[MAX_HASH_LENGTH + 20];
-    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", PADS_DIR, pad_hash);
+    snprintf(state_filename, sizeof(state_filename), "%s/%s.state", PADS_DIR, pad_chksum);
     
     FILE* state_file = fopen(state_filename, "wb");
     if (!state_file) {
@@ -1106,52 +1116,53 @@ int write_state_offset(const char* pad_hash, uint64_t offset) {
     return 0;
 }
 
-int calculate_sha256(const char* filename, char* hash_hex) {
+int calculate_checksum(const char* filename, char* checksum_hex) {
     FILE* file = fopen(filename, "rb");
     if (!file) {
         return 1;
     }
     
-    EVP_MD_CTX* mdctx = EVP_MD_CTX_new();
-    if (!mdctx) {
-        fclose(file);
-        return 1;
-    }
-    
-    if (EVP_DigestInit_ex(mdctx, EVP_sha256(), NULL) != 1) {
-        EVP_MD_CTX_free(mdctx);
-        fclose(file);
-        return 1;
-    }
-    
+    unsigned char checksum[32];
     unsigned char buffer[64 * 1024];  // 64KB buffer for large files
     size_t bytes_read;
     
+    // Initialize checksum
+    memset(checksum, 0, 32);
+    size_t total_bytes = 0;
+    
+    // Calculate XOR checksum of entire file
     while ((bytes_read = fread(buffer, 1, sizeof(buffer), file)) > 0) {
-        if (EVP_DigestUpdate(mdctx, buffer, bytes_read) != 1) {
-            EVP_MD_CTX_free(mdctx);
+        // Process this chunk with XOR checksum
+        for (size_t i = 0; i < bytes_read; i++) {
+            unsigned char bucket = (total_bytes + i) % 32;
+            checksum[bucket] ^= buffer[i] ^ (((total_bytes + i) >> 8) & 0xFF) ^ 
+                               (((total_bytes + i) >> 16) & 0xFF) ^ (((total_bytes + i) >> 24) & 0xFF);
+        }
+        total_bytes += bytes_read;
+    }
+    
+    fclose(file);
+    
+    // Now encrypt the checksum with the first 32 bytes of the pad
+    fseek(file = fopen(filename, "rb"), 0, SEEK_SET);
+    unsigned char pad_key[32];
+    if (fread(pad_key, 1, 32, file) != 32) {
         fclose(file);
         return 1;
     }
-    }
-    
-    unsigned char hash[EVP_MAX_MD_SIZE];
-    unsigned int hash_len;
-    
-    if (EVP_DigestFinal_ex(mdctx, hash, &hash_len) != 1) {
-        EVP_MD_CTX_free(mdctx);
-        fclose(file);
-        return 1;
-    }
-    
-    EVP_MD_CTX_free(mdctx);
     fclose(file);
     
-    // Convert to hex string
-    for (unsigned int i = 0; i < hash_len; i++) {
-        sprintf(hash_hex + (i * 2), "%02x", hash[i]);
+    // XOR encrypt the checksum with pad data to create unique identifier
+    unsigned char encrypted_checksum[32];
+    for (int i = 0; i < 32; i++) {
+        encrypted_checksum[i] = checksum[i] ^ pad_key[i];
     }
-    hash_hex[hash_len * 2] = '\0';
+    
+    // Convert to hex string (64 characters)
+    for (int i = 0; i < 32; i++) {
+        sprintf(checksum_hex + (i * 2), "%02x", encrypted_checksum[i]);
+    }
+    checksum_hex[64] = '\0';
     
     return 0;
 }
@@ -1226,49 +1237,6 @@ int collect_keyboard_entropy(unsigned char* entropy_buffer, size_t max_size, siz
     return 0;
 }
 
-int hkdf_expand(const unsigned char* prk, size_t prk_len, 
-                const unsigned char* info, size_t info_len,
-                unsigned char* okm, size_t okm_len) {
-    EVP_MD_CTX* ctx = EVP_MD_CTX_new();
-    if (!ctx) return 1;
-    
-    unsigned char t[32]; // SHA-256 output size
-    unsigned char counter = 1;
-    size_t t_len = 32;
-    size_t pos = 0;
-    
-    while (pos < okm_len) {
-        if (EVP_DigestInit_ex(ctx, EVP_sha256(), NULL) != 1) {
-            EVP_MD_CTX_free(ctx);
-            return 1;
-        }
-        
-        if (pos > 0) {
-            EVP_DigestUpdate(ctx, t, t_len);
-        }
-        
-        EVP_DigestUpdate(ctx, prk, prk_len);
-        if (info && info_len > 0) {
-            EVP_DigestUpdate(ctx, info, info_len);
-        }
-        EVP_DigestUpdate(ctx, &counter, 1);
-        
-        unsigned int hash_len;
-        if (EVP_DigestFinal_ex(ctx, t, &hash_len) != 1) {
-            EVP_MD_CTX_free(ctx);
-            return 1;
-        }
-        
-        size_t copy_len = (okm_len - pos < hash_len) ? okm_len - pos : hash_len;
-        memcpy(okm + pos, t, copy_len);
-        
-        pos += copy_len;
-        counter++;
-    }
-    
-    EVP_MD_CTX_free(ctx);
-    return 0;
-}
 
 // Directory management functions
 int ensure_pads_directory(void) {
@@ -1281,54 +1249,96 @@ int ensure_pads_directory(void) {
     return 0;
 }
 
-void get_pad_path(const char* hash, char* pad_path, char* state_path) {
-    snprintf(pad_path, MAX_HASH_LENGTH + 20, "%s/%s.pad", PADS_DIR, hash);
-    snprintf(state_path, MAX_HASH_LENGTH + 20, "%s/%s.state", PADS_DIR, hash);
+void get_pad_path(const char* chksum, char* pad_path, char* state_path) {
+    snprintf(pad_path, MAX_HASH_LENGTH + 20, "%s/%s.pad", PADS_DIR, chksum);
+    snprintf(state_path, MAX_HASH_LENGTH + 20, "%s/%s.state", PADS_DIR, chksum);
 }
 
-char* base64_encode(const unsigned char* input, int length) {
-    BIO *bio, *b64;
-    BUF_MEM *buffer_ptr;
 
-    b64 = BIO_new(BIO_f_base64());
-    bio = BIO_new(BIO_s_mem());
-    bio = BIO_push(b64, bio);
-    
-    BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);
-    BIO_write(bio, input, length);
-    BIO_flush(bio);
-    
-    BIO_get_mem_ptr(bio, &buffer_ptr);
-    
-    char* result = malloc(buffer_ptr->length + 1);
-    memcpy(result, buffer_ptr->data, buffer_ptr->length);
-    result[buffer_ptr->length] = '\0';
-    
-    BIO_free_all(bio);
-    return result;
+// Custom XOR checksum function
+void xor_checksum_256(const unsigned char* data, size_t len, unsigned char checksum[32]) {
+    memset(checksum, 0, 32);
+    for (size_t i = 0; i < len; i++) {
+        unsigned char bucket = i % 32;
+        checksum[bucket] ^= data[i] ^ ((i >> 8) & 0xFF) ^ ((i >> 16) & 0xFF) ^ ((i >> 24) & 0xFF);
+    }
 }
 
-unsigned char* base64_decode(const char* input, int* output_length) {
-    BIO *bio, *b64;
-    int decode_len = strlen(input);
+// Custom base64 encode function
+char* custom_base64_encode(const unsigned char* input, int length) {
+    int output_length = 4 * ((length + 2) / 3);
+    char* encoded = malloc(output_length + 1);
+    if (!encoded) return NULL;
     
-    unsigned char* buffer = malloc(decode_len);
+    int i, j;
+    for (i = 0, j = 0; i < length;) {
+        uint32_t octet_a = i < length ? input[i++] : 0;
+        uint32_t octet_b = i < length ? input[i++] : 0;
+        uint32_t octet_c = i < length ? input[i++] : 0;
         
-    bio = BIO_new_mem_buf(input, -1);
-    b64 = BIO_new(BIO_f_base64());
-    bio = BIO_push(b64, bio);
+        uint32_t triple = (octet_a << 16) + (octet_b << 8) + octet_c;
         
-    BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);
-    *output_length = BIO_read(bio, buffer, decode_len);
+        encoded[j++] = base64_chars[(triple >> 18) & 63];
+        encoded[j++] = base64_chars[(triple >> 12) & 63];
+        encoded[j++] = base64_chars[(triple >> 6) & 63];
+        encoded[j++] = base64_chars[triple & 63];
+    }
     
-    BIO_free_all(bio);
+    // Add padding
+    for (int pad = 0; pad < (3 - length % 3) % 3; pad++) {
+        encoded[output_length - 1 - pad] = '=';
+    }
     
-    if (*output_length <= 0) {
-        free(buffer);
+    encoded[output_length] = '\0';
+    return encoded;
+}
+
+// Custom base64 decode function
+unsigned char* custom_base64_decode(const char* input, int* output_length) {
+    int input_length = strlen(input);
+    if (input_length % 4 != 0) return NULL;
+    
+    *output_length = input_length / 4 * 3;
+    if (input[input_length - 1] == '=') (*output_length)--;
+    if (input[input_length - 2] == '=') (*output_length)--;
+    
+    unsigned char* decoded = malloc(*output_length);
+    if (!decoded) return NULL;
+    
+    int i, j;
+    for (i = 0, j = 0; i < input_length;) {
+        int sextet_a = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
+        int sextet_b = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
+        int sextet_c = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
+        int sextet_d = input[i] == '=' ? 0 & i++ : base64_decode_table[(unsigned char)input[i++]];
+        
+        if (sextet_a == -1 || sextet_b == -1 || sextet_c == -1 || sextet_d == -1) {
+            free(decoded);
             return NULL;
         }
         
-    return buffer;
+        uint32_t triple = (sextet_a << 18) + (sextet_b << 12) + (sextet_c << 6) + sextet_d;
+        
+        if (j < *output_length) decoded[j++] = (triple >> 16) & 255;
+        if (j < *output_length) decoded[j++] = (triple >> 8) & 255;
+        if (j < *output_length) decoded[j++] = triple & 255;
+    }
+    
+    return decoded;
+}
+
+// Simple keyboard entropy mixing function
+void simple_entropy_mix(unsigned char* urandom_buffer, size_t buffer_size, 
+                        const unsigned char* entropy_data, size_t entropy_size) {
+    if (!entropy_data || entropy_size == 0) return;
+    
+    for (size_t i = 0; i < buffer_size; i++) {
+        // XOR with entropy data in a rotating pattern
+        unsigned char entropy_byte = entropy_data[i % entropy_size];
+        // Mix position information
+        entropy_byte ^= (i & 0xFF) ^ ((i >> 8) & 0xFF);
+        urandom_buffer[i] ^= entropy_byte;
+    }
 }
 
 void print_usage(const char* program_name) {
@@ -1337,9 +1347,9 @@ void print_usage(const char* program_name) {
     printf("Usage:\n");
     printf("  %s                              - Interactive mode\n", program_name);
     printf("  %s generate <size>              - Generate new pad\n", program_name);
-    printf("  %s encrypt <pad_hash_prefix>    - Encrypt text\n", program_name);
-    printf("  %s decrypt <pad_hash_prefix>    - Decrypt message\n", program_name);
+    printf("  %s encrypt <pad_checksum_prefix> - Encrypt text\n", program_name);
+    printf("  %s decrypt <pad_checksum_prefix> - Decrypt message\n", program_name);
     printf("  %s list                         - List available pads\n", program_name);
     printf("\nSize examples: 1GB, 5TB, 512MB, 2048 (bytes)\n");
-    printf("Pad selection: Full hash, prefix, or number from list\n");
+    printf("Pad selection: Full chksum, prefix, or number from list\n");
 }