Version v0.2.18 - Remove original filename from binary .otp file format - simplify file structure

.clinerules/workspace_rules.md

@@ -0,0 +1,4 @@
+
+When building, use build.sh, not make. 
+
+Use it as follows: build.sh -m "useful comment on changes being made"

.gitignore

@@ -1,6 +1,7 @@
 otp
 pads/
 Gemini.md
+TropicOfCancer-HenryMiller.txt
 
 # Auto-generated version files
 src/version.h

README.md

@@ -1,11 +1,14 @@
-r# OTP Cipher - One Time Pad Implementation
+# OTP Cipher - One Time Pad Implementation
 
 A secure one-time pad (OTP) cipher implementation in C with automatic versioning system.
 
 ## Features
 
 - **Perfect Security**: Implements true one-time pad encryption with information-theoretic security
+- **Text & File Encryption**: Supports both inline text and file encryption
+- **Multiple Output Formats**: Binary (.otp) and ASCII armored (.otp.asc) file formats
 - **Keyboard Entropy**: Optional keyboard entropy collection for enhanced randomness
+- **Short Command Flags**: Convenient single-character flags for all operations
 - **Automatic Versioning**: Built-in semantic versioning with automatic patch increment
 - **Multiple Build Options**: Standard and static linking builds
 - **Cross-Platform**: Works on Linux and other UNIX-like systems
@@ -148,45 +151,124 @@ otp/
 └── VERSION          # Plain text version (generated)
 ```
 
-## Examples
+## File Formats
+
+### .otp File Format (Binary)
+
+Binary encrypted files use a structured header format:
+
+```
+Offset | Size | Field               | Description
+-------|------|-------------------|----------------------------------
+0      | 4    | Magic             | "OTP\0" - File type identifier
+4      | 2    | Version           | Format version (currently 1)
+6      | 32   | Pad Checksum      | Binary pad checksum (32 bytes)
+38     | 8    | Pad Offset        | Offset in pad file (uint64_t)
+46     | 2    | Filename Length   | Original filename length (uint16_t)
+48     | var  | Original Filename | Original filename string
+var    | 4    | File Mode         | Original file permissions (uint32_t)
+var    | 8    | File Size         | Original file size (uint64_t)
+var    | var  | Encrypted Data    | XOR-encrypted file contents
+```
+
+### .otp.asc File Format (ASCII Armored)
+
+ASCII armored files use the same format as encrypted text messages:
+
+```
+-----BEGIN OTP MESSAGE-----
+Version: v0.2.15
+Pad-ChkSum: <64-character-hex-checksum>
+Pad-Offset: <decimal-offset-value>
+
+<base64-encoded-encrypted-data>
+-----END OTP MESSAGE-----
+```
+
+**Note:** ASCII armored files lose original filename and permission metadata.
+
+## Usage Examples
+
+### Short Command Flags
+```bash
+# Quick commands using short flags
+./otp -g 1GB                    # Generate 1GB pad
+./otp -l                        # List available pads
+./otp -e 1a2b "Hello world"     # Encrypt text inline
+./otp -d "-----BEGIN OTP..."    # Decrypt message inline
+
+# File operations
+./otp -f document.pdf 1a2b                # Encrypt file (binary)
+./otp -f document.pdf 1a2b -a             # Encrypt file (ASCII)
+./otp -f document.pdf 1a2b -o secret.otp  # Custom output name
+```
+
+### Text Encryption
+```bash
+# Interactive text encryption
+./otp encrypt 1a2b3c
+Enter text to encrypt: This is my secret message
+# Outputs ASCII armored message
+
+# Inline text encryption
+./otp -e 1a2b3c "This is my secret message"
+# Outputs ASCII armored message immediately
+```
+
+### File Encryption
+```bash
+# Binary format (preserves metadata)
+./otp -f sensitive.doc a1b2c3
+
+# ASCII armored format (text-safe)
+./otp -f sensitive.doc a1b2c3 -a
+
+# Custom output filename
+./otp -f sensitive.doc a1b2c3 -o encrypted_document.otp
+```
+
+### Decryption
+```bash
+# Auto-detect format and pad from message/file
+./otp -d encrypted.otp.asc
+./otp -d "-----BEGIN OTP MESSAGE-----..."
+
+# Interactive mode
+./otp decrypt
+# Prompts for encrypted message input
+```
 
 ### Build and Version Tracking
 ```bash
 $ ./build.sh build
 [INFO] Incrementing version...
-[INFO] Current version: v0.1.4  
+[INFO] Current version: v0.2.14
-[INFO] New version: v0.1.5
+[INFO] New version: v0.2.15
-[SUCCESS] Created new version tag: v0.1.5
+[SUCCESS] Created new version tag: v0.2.15
 [SUCCESS] Build completed successfully
 
-$ ./otp
-=== OTP Cipher v0.1.5 ===
-
-=== Main Menu ===
-1. Generate new pad
-2. Encrypt message
-3. Decrypt message
-4. List available pads
-5. Show pad information
-6. Exit
-
 $ ./otp --help
-OTP Cipher - One Time Pad Implementation v0.1.5
+OTP Cipher - One Time Pad Implementation v0.2.15
-Built on 2025-08-10 at 08:17:47 from commit 9edfa5f on branch master
+Built on 2025-08-10 at 14:07:58 from commit ae0afcf on branch master
-Usage:
-  ./otp                              - Interactive mode
-  ...
 ```
 
-### Version History
+### Advanced Features
 ```bash
-$ git tag --list
+# Generate pad with keyboard entropy
-v0.1.0
+./otp generate 5GB
-v0.1.1  
+# Follow prompts for keyboard entropy collection
-v0.1.2
+
-v0.1.3
+# Check pad usage
-v0.1.4
+./otp -l
-v0.1.5
+Available pads:
+No.  ChkSum (first 16 chars) Size         Used         % Used
+---  -------------------   ----------   ----------   ------
+1    97d9d82b5414a943      1.00GB       156B         0.0%
+2    0c8e19fde996e683      1000B        248B         24.8%
+
+# Show detailed pad information
+./otp
+# Select "S" for show pad info, enter checksum or prefix
 ```
 
 ## License
@@ -199,5 +281,3 @@ When contributing:
 1. The version will automatically increment on builds
 2. For major features, consider manually creating minor version tags
 3. Generated version files (`src/version.*`, `VERSION`) should not be committed
-# Test change
-# Testing -m flag

debug.c

@@ -0,0 +1 @@
+int main() { printf("Testing direct filename: %d\n", strncmp("97d9d82b5414a9439102f3811fb90ab1d6368a00d33229a18b306476f9d04f82.pad", "97", 2)); return 0; }

otp.c

@@ -52,6 +52,10 @@ int generate_pad(uint64_t size_bytes, int show_progress);
 int generate_pad_with_entropy(uint64_t size_bytes, int show_progress, int use_keyboard_entropy);
 int encrypt_text(const char* pad_identifier, const char* input_text);
 int decrypt_text(const char* pad_identifier, const char* encrypted_message);
+int encrypt_file(const char* pad_identifier, const char* input_file, const char* output_file, int ascii_armor);
+int decrypt_file(const char* input_file, const char* output_file);
+int decrypt_binary_file(FILE* input_fp, const char* output_file);
+int decrypt_ascii_file(const char* input_file, const char* output_file);
 
 // Keyboard entropy functions
 int setup_raw_terminal(struct termios* original_termios);
@@ -147,9 +151,9 @@ int interactive_mode(void) {
 }
 
 int command_line_mode(int argc, char* argv[]) {
-    if (strcmp(argv[1], "generate") == 0) {
+    if (strcmp(argv[1], "generate") == 0 || strcmp(argv[1], "-g") == 0) {
         if (argc != 3) {
-            printf("Usage: %s generate <size>\n", argv[0]);
+            printf("Usage: %s generate|-g <size>\n", argv[0]);
             printf("Size examples: 1024, 1GB, 5TB, 512MB\n");
             return 1;
         }
@@ -160,25 +164,80 @@ int command_line_mode(int argc, char* argv[]) {
         }
         return generate_pad_with_entropy(size, 1, 0);  // No keyboard entropy for command line
     }
-    else if (strcmp(argv[1], "encrypt") == 0) {
+    else if (strcmp(argv[1], "encrypt") == 0 || strcmp(argv[1], "-e") == 0) {
         if (argc < 3 || argc > 4) {
-            printf("Usage: %s encrypt <pad_chksum_or_prefix> [text_to_encrypt]\n", argv[0]);
+            printf("Usage: %s encrypt|-e <pad_chksum_or_prefix> [text_to_encrypt]\n", argv[0]);
             return 1;
         }
         // Pass text if provided, otherwise NULL for interactive mode
         const char* text = (argc == 4) ? argv[3] : NULL;
         return encrypt_text(argv[2], text);
     }
-    else if (strcmp(argv[1], "decrypt") == 0) {
+    else if (strcmp(argv[1], "decrypt") == 0 || strcmp(argv[1], "-d") == 0) {
-        if (argc < 3 || argc > 4) {
+        if (argc == 2) {
-            printf("Usage: %s decrypt <pad_chksum_or_prefix> [encrypted_message]\n", argv[0]);
+            // Interactive mode - no arguments needed
+            return decrypt_text(NULL, NULL);
+        }
+        else if (argc == 3) {
+            // Check if the argument looks like an encrypted message (starts with -----)
+            if (strncmp(argv[2], "-----BEGIN OTP MESSAGE-----", 27) == 0) {
+                // Inline decrypt with message only
+                return decrypt_text(NULL, argv[2]);
+            } else {
+                // Check if it's a file (contains . or ends with known extensions)
+                if (strstr(argv[2], ".") != NULL) {
+                    // Treat as file
+                    return decrypt_file(argv[2], NULL);
+                } else {
+                    // Interactive decrypt with pad hint (legacy support)
+                    return decrypt_text(argv[2], NULL);
+                }
+            }
+        }
+        else if (argc == 4) {
+            // Check for -o flag for output file
+            if (strcmp(argv[2], "-o") == 0) {
+                printf("Usage: %s decrypt|-d <input_file> [-o <output_file>]\n", argv[0]);
+                return 1;
+            } else {
+                // Legacy format: pad_chksum and message, or file with output
+                return decrypt_text(argv[2], argv[3]);
+            }
+        }
+        else if (argc == 5 && strcmp(argv[3], "-o") == 0) {
+            // File decryption with output: -d <input_file> -o <output_file>
+            return decrypt_file(argv[2], argv[4]);
+        }
+        else {
+            printf("Usage: %s decrypt|-d [encrypted_message|file] [-o output_file]\n", argv[0]);
+            printf("       %s decrypt|-d [encrypted_message]  (pad info from message)\n", argv[0]);
             return 1;
         }
-        // Pass message if provided, otherwise NULL for interactive mode
-        const char* message = (argc == 4) ? argv[3] : NULL;
-        return decrypt_text(argv[2], message);
     }
-    else if (strcmp(argv[1], "list") == 0) {
+    else if (strcmp(argv[1], "-f") == 0) {
+        // File encryption mode: -f <input_file> <pad_prefix> [-a] [-o <output_file>]
+        if (argc < 4) {
+            printf("Usage: %s -f <input_file> <pad_prefix> [-a] [-o <output_file>]\n", argv[0]);
+            return 1;
+        }
+        
+        const char* input_file = argv[2];
+        const char* pad_prefix = argv[3];
+        int ascii_armor = 0;
+        const char* output_file = NULL;
+        
+        // Parse optional flags
+        for (int i = 4; i < argc; i++) {
+            if (strcmp(argv[i], "-a") == 0) {
+                ascii_armor = 1;
+            } else if (strcmp(argv[i], "-o") == 0 && i + 1 < argc) {
+                output_file = argv[++i];
+            }
+        }
+        
+        return encrypt_file(pad_prefix, input_file, output_file, ascii_armor);
+    }
+    else if (strcmp(argv[1], "list") == 0 || strcmp(argv[1], "-l") == 0) {
         return list_available_pads();
     }
     else {
@@ -306,41 +365,53 @@ uint64_t parse_size_string(const char* size_str) {
 
 char* find_pad_by_prefix(const char* prefix) {
     DIR* dir = opendir(PADS_DIR);
-    if (!dir) return NULL;
+    if (!dir) {
+        printf("Error: Cannot open pads directory\n");
+        return NULL;
+    }
     
     struct dirent* entry;
     char* matches[100];  // Store up to 100 matches
     int match_count = 0;
     
     // Check if it's a number (for interactive menu selection)
+    // Only treat as number if it's a single digit (1-9) to avoid conflicts with hex prefixes
     char* endptr;
     int selection = strtol(prefix, &endptr, 10);
-    if (*endptr == '\0' && selection > 0) {
+    if (*endptr == '\0' && selection > 0 && selection <= 9 && strlen(prefix) == 1) {
         // It's a number, find the nth pad
         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 chksum + ".pad"
+            // Skip . and .. entries, and only process .pad files
-                current++;
+            if (entry->d_name[0] == '.') continue;
-                if (current == selection) {
+            if (!strstr(entry->d_name, ".pad")) continue;
-                    matches[match_count] = malloc(65);
+            if (strlen(entry->d_name) != 68) continue; // 64 char chksum + ".pad"
-                    strncpy(matches[match_count], entry->d_name, 64);
+            
-                    matches[match_count][64] = '\0';
+            current++;
-                    match_count = 1;
+            if (current == selection) {
-                }
+                matches[match_count] = malloc(65);
+                strncpy(matches[match_count], entry->d_name, 64);
+                matches[match_count][64] = '\0';
+                match_count = 1;
+                break;
             }
         }
     } else {
         // Find pads that start with the prefix
         size_t prefix_len = strlen(prefix);
         while ((entry = readdir(dir)) != NULL && match_count < 100) {
-            if (strstr(entry->d_name, ".pad") && strlen(entry->d_name) == 68) {
+            // Skip . and .. entries, and only process .pad files
-                if (strncmp(entry->d_name, prefix, prefix_len) == 0) {
+            if (entry->d_name[0] == '.') continue;
-                    matches[match_count] = malloc(65);
+            if (!strstr(entry->d_name, ".pad")) continue;
-                    strncpy(matches[match_count], entry->d_name, 64);
+            if (strlen(entry->d_name) != 68) continue; // 64 char chksum + ".pad"
-                    matches[match_count][64] = '\0';
+            
-                    match_count++;
+            // Compare prefix with the filename (checksum part)
-                }
+            if (strncmp(entry->d_name, prefix, prefix_len) == 0) {
+                matches[match_count] = malloc(65);
+                strncpy(matches[match_count], entry->d_name, 64);
+                matches[match_count][64] = '\0';
+                match_count++;
             }
         }
     }
@@ -359,14 +430,35 @@ char* find_pad_by_prefix(const char* prefix) {
         printf("Multiple matches found for '%s':\n", prefix);
         for (int i = 0; i < match_count; i++) {
             printf("%d. %.16s...\n", i + 1, matches[i]);
-            if (i > 0) free(matches[i]);
         }
-        printf("Please be more specific.\n");
+        printf("Please be more specific or enter a number (1-%d): ", match_count);
-        char* result = matches[0];
+        fflush(stdout);
-        for (int i = 1; i < match_count; i++) {
+        
+        char choice_input[64];
+        if (fgets(choice_input, sizeof(choice_input), stdin)) {
+            choice_input[strcspn(choice_input, "\n")] = 0;
+            
+            // Check if it's a number
+            char* endptr;
+            int choice = strtol(choice_input, &endptr, 10);
+            if (*endptr == '\0' && choice >= 1 && choice <= match_count) {
+                // Valid choice, return selected pad
+                char* result = matches[choice - 1];
+                // Free the others
+                for (int i = 0; i < match_count; i++) {
+                    if (i != choice - 1) {
+                        free(matches[i]);
+                    }
+                }
+                return result;
+            }
+        }
+        
+        // Invalid choice or no input, free all and return NULL
+        for (int i = 0; i < match_count; i++) {
             free(matches[i]);
         }
-        return result;
+        return NULL;
     }
 }
 
@@ -1128,6 +1220,573 @@ int decrypt_text(const char* pad_identifier, const char* encrypted_message) {
     return 0;
 }
 
+int encrypt_file(const char* pad_identifier, const char* input_file, const char* output_file, int ascii_armor) {
+    char* pad_chksum = find_pad_by_prefix(pad_identifier);
+    if (!pad_chksum) {
+        return 1;
+    }
+    
+    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_chksum, pad_path, state_path);
+    
+    // Check if input file exists and get its size
+    struct stat input_stat;
+    if (stat(input_file, &input_stat) != 0) {
+        printf("Error: Input file %s not found\n", input_file);
+        free(pad_chksum);
+        return 1;
+    }
+    
+    uint64_t file_size = input_stat.st_size;
+    if (file_size == 0) {
+        printf("Error: Input file is empty\n");
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Check if pad file exists
+    if (access(pad_path, R_OK) != 0) {
+        printf("Error: Pad file %s not found\n", pad_path);
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Read current offset
+    if (read_state_offset(pad_chksum, &current_offset) != 0) {
+        printf("Error: Cannot read state file\n");
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Ensure we never encrypt before offset 32
+    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;
+    }
+    
+    // Check if we have enough pad space
+    struct stat pad_stat;
+    if (stat(pad_path, &pad_stat) != 0) {
+        printf("Error: Cannot get pad file size\n");
+        free(pad_chksum);
+        return 1;
+    }
+    
+    if (current_offset + file_size > (uint64_t)pad_stat.st_size) {
+        printf("Error: Not enough pad space remaining\n");
+        printf("Need: %lu bytes, Available: %lu bytes\n", 
+               file_size, (uint64_t)pad_stat.st_size - current_offset);
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Generate output filename if not specified
+    char default_output[512];
+    if (output_file == NULL) {
+        if (ascii_armor) {
+            snprintf(default_output, sizeof(default_output), "%s.otp.asc", input_file);
+        } else {
+            snprintf(default_output, sizeof(default_output), "%s.otp", input_file);
+        }
+        output_file = default_output;
+    }
+    
+    // Open input file
+    FILE* input_fp = fopen(input_file, "rb");
+    if (!input_fp) {
+        printf("Error: Cannot open input file %s\n", input_file);
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Open pad file
+    FILE* pad_file = fopen(pad_path, "rb");
+    if (!pad_file) {
+        printf("Error: Cannot open pad file\n");
+        fclose(input_fp);
+        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(input_fp);
+        fclose(pad_file);
+        free(pad_chksum);
+        return 1;
+    }
+    
+    // Read and encrypt file
+    unsigned char buffer[64 * 1024];
+    unsigned char pad_buffer[64 * 1024];
+    unsigned char* encrypted_data = malloc(file_size);
+    uint64_t bytes_processed = 0;
+    time_t start_time = time(NULL);
+    
+    printf("Encrypting %s...\n", input_file);
+    
+    while (bytes_processed < file_size) {
+        uint64_t chunk_size = sizeof(buffer);
+        if (file_size - bytes_processed < chunk_size) {
+            chunk_size = file_size - bytes_processed;
+        }
+        
+        // Read file data
+        if (fread(buffer, 1, chunk_size, input_fp) != chunk_size) {
+            printf("Error: Cannot read input file data\n");
+            free(encrypted_data);
+            fclose(input_fp);
+            fclose(pad_file);
+            free(pad_chksum);
+            return 1;
+        }
+        
+        // Read pad data
+        if (fread(pad_buffer, 1, chunk_size, pad_file) != chunk_size) {
+            printf("Error: Cannot read pad data\n");
+            free(encrypted_data);
+            fclose(input_fp);
+            fclose(pad_file);
+            free(pad_chksum);
+            return 1;
+        }
+        
+        // XOR encrypt
+        for (uint64_t i = 0; i < chunk_size; i++) {
+            encrypted_data[bytes_processed + i] = buffer[i] ^ pad_buffer[i];
+        }
+        
+        bytes_processed += chunk_size;
+        
+        // Show progress for large files (> 10MB)
+        if (file_size > 10 * 1024 * 1024 && bytes_processed % (1024 * 1024) == 0) {
+            show_progress(bytes_processed, file_size, start_time);
+        }
+    }
+    
+    if (file_size > 10 * 1024 * 1024) {
+        show_progress(file_size, file_size, start_time);
+        printf("\n");
+    }
+    
+    fclose(input_fp);
+    fclose(pad_file);
+    
+    // Write output file
+    if (ascii_armor) {
+        // ASCII armored format - same as message format
+        FILE* output_fp = fopen(output_file, "w");
+        if (!output_fp) {
+            printf("Error: Cannot create output file %s\n", output_file);
+            free(encrypted_data);
+            free(pad_chksum);
+            return 1;
+        }
+        
+        // Encode as base64
+        char* base64_data = custom_base64_encode(encrypted_data, file_size);
+        
+        // Write ASCII armor
+        fprintf(output_fp, "-----BEGIN OTP MESSAGE-----\n");
+        fprintf(output_fp, "Version: %s\n", get_version());
+        fprintf(output_fp, "Pad-ChkSum: %s\n", chksum_hex);
+        fprintf(output_fp, "Pad-Offset: %lu\n", current_offset);
+        fprintf(output_fp, "\n");
+        
+        // Write base64 data in 64-character lines
+        int b64_len = strlen(base64_data);
+        for (int i = 0; i < b64_len; i += 64) {
+            fprintf(output_fp, "%.64s\n", base64_data + i);
+        }
+        
+        fprintf(output_fp, "-----END OTP MESSAGE-----\n");
+        
+        fclose(output_fp);
+        free(base64_data);
+    } else {
+        // Binary format
+        FILE* output_fp = fopen(output_file, "wb");
+        if (!output_fp) {
+            printf("Error: Cannot create output file %s\n", output_file);
+            free(encrypted_data);
+            free(pad_chksum);
+            return 1;
+        }
+        
+        // Write binary header
+        // Magic: "OTP\0"
+        fwrite("OTP\0", 1, 4, output_fp);
+        
+        // Version: 2 bytes
+        uint16_t version = 1;
+        fwrite(&version, sizeof(uint16_t), 1, output_fp);
+        
+        // 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]);
+        }
+        fwrite(pad_chksum_bin, 1, 32, output_fp);
+        
+        // Pad offset: 8 bytes
+        fwrite(&current_offset, sizeof(uint64_t), 1, output_fp);
+        
+        
+        // File mode: 4 bytes
+        uint32_t file_mode = input_stat.st_mode;
+        fwrite(&file_mode, sizeof(uint32_t), 1, output_fp);
+        
+        // File size: 8 bytes
+        fwrite(&file_size, sizeof(uint64_t), 1, output_fp);
+        
+        // Encrypted data
+        fwrite(encrypted_data, 1, file_size, output_fp);
+        
+        fclose(output_fp);
+    }
+    
+    // Update state offset
+    if (write_state_offset(pad_chksum, current_offset + file_size) != 0) {
+        printf("Warning: Failed to update state file\n");
+    }
+    
+    printf("File encrypted successfully: %s\n", output_file);
+    if (ascii_armor) {
+        printf("Format: ASCII armored (.otp.asc)\n");
+    } else {
+        printf("Format: Binary (.otp)\n");
+    }
+    
+    // Cleanup
+    free(encrypted_data);
+    free(pad_chksum);
+    
+    return 0;
+}
+
+int decrypt_file(const char* input_file, const char* output_file) {
+    // Check if input file exists
+    if (access(input_file, R_OK) != 0) {
+        printf("Error: Input file %s not found\n", input_file);
+        return 1;
+    }
+    
+    FILE* input_fp = fopen(input_file, "rb");
+    if (!input_fp) {
+        printf("Error: Cannot open input file %s\n", input_file);
+        return 1;
+    }
+    
+    // Read first few bytes to determine format
+    char magic[4];
+    if (fread(magic, 1, 4, input_fp) != 4) {
+        printf("Error: Cannot read file header\n");
+        fclose(input_fp);
+        return 1;
+    }
+    
+    fseek(input_fp, 0, SEEK_SET); // Reset to beginning
+    
+    if (memcmp(magic, "OTP\0", 4) == 0) {
+        // Binary format
+        return decrypt_binary_file(input_fp, output_file);
+    } else {
+        // Assume ASCII armored format, read entire file as text
+        fclose(input_fp);
+        return decrypt_ascii_file(input_file, output_file);
+    }
+}
+
+int decrypt_binary_file(FILE* input_fp, const char* output_file) {
+    // Read binary header
+    char magic[4];
+    uint16_t version;
+    unsigned char pad_chksum_bin[32];
+    uint64_t pad_offset;
+    uint32_t file_mode;
+    uint64_t file_size;
+    
+    if (fread(magic, 1, 4, input_fp) != 4 ||
+        fread(&version, sizeof(uint16_t), 1, input_fp) != 1 ||
+        fread(pad_chksum_bin, 1, 32, input_fp) != 32 ||
+        fread(&pad_offset, sizeof(uint64_t), 1, input_fp) != 1 ||
+        fread(&file_mode, sizeof(uint32_t), 1, input_fp) != 1 ||
+        fread(&file_size, sizeof(uint64_t), 1, input_fp) != 1) {
+        printf("Error: Cannot read binary header\n");
+        fclose(input_fp);
+        return 1;
+    }
+    
+    if (memcmp(magic, "OTP\0", 4) != 0) {
+        printf("Error: Invalid binary format\n");
+        fclose(input_fp);
+        return 1;
+    }
+    
+    // Convert binary checksum to hex
+    char pad_chksum_hex[65];
+    for (int i = 0; i < 32; i++) {
+        sprintf(pad_chksum_hex + i*2, "%02x", pad_chksum_bin[i]);
+    }
+    pad_chksum_hex[64] = '\0';
+    
+    printf("Decrypting binary file...\n");
+    printf("File size: %lu bytes\n", file_size);
+    
+    // Check if we have the required pad
+    char pad_path[MAX_HASH_LENGTH + 20];
+    char state_path[MAX_HASH_LENGTH + 20];
+    get_pad_path(pad_chksum_hex, pad_path, state_path);
+    
+    if (access(pad_path, R_OK) != 0) {
+        printf("Error: Required pad not found: %s\n", pad_chksum_hex);
+        printf("Available pads:\n");
+        list_available_pads();
+        fclose(input_fp);
+        return 1;
+    }
+    
+    // Determine output filename
+    char default_output[512];
+    if (output_file == NULL) {
+        snprintf(default_output, sizeof(default_output), "decrypted.bin");
+        output_file = default_output;
+    }
+    
+    // Read encrypted data
+    unsigned char* encrypted_data = malloc(file_size);
+    if (fread(encrypted_data, 1, file_size, input_fp) != file_size) {
+        printf("Error: Cannot read encrypted data\n");
+        free(encrypted_data);
+        fclose(input_fp);
+        return 1;
+    }
+    fclose(input_fp);
+    
+    // Open pad file and decrypt
+    FILE* pad_file = fopen(pad_path, "rb");
+    if (!pad_file) {
+        printf("Error: Cannot open pad file\n");
+        free(encrypted_data);
+        return 1;
+    }
+    
+    if (fseek(pad_file, pad_offset, SEEK_SET) != 0) {
+        printf("Error: Cannot seek to offset in pad file\n");
+        free(encrypted_data);
+        fclose(pad_file);
+        return 1;
+    }
+    
+    unsigned char* pad_data = malloc(file_size);
+    if (fread(pad_data, 1, file_size, pad_file) != file_size) {
+        printf("Error: Cannot read pad data\n");
+        free(encrypted_data);
+        free(pad_data);
+        fclose(pad_file);
+        return 1;
+    }
+    fclose(pad_file);
+    
+    // XOR decrypt
+    for (uint64_t i = 0; i < file_size; i++) {
+        encrypted_data[i] ^= pad_data[i];
+    }
+    
+    // Write decrypted file
+    FILE* output_fp = fopen(output_file, "wb");
+    if (!output_fp) {
+        printf("Error: Cannot create output file %s\n", output_file);
+        free(encrypted_data);
+        free(pad_data);
+        return 1;
+    }
+    
+    if (fwrite(encrypted_data, 1, file_size, output_fp) != file_size) {
+        printf("Error: Cannot write decrypted data\n");
+        free(encrypted_data);
+        free(pad_data);
+        fclose(output_fp);
+        return 1;
+    }
+    fclose(output_fp);
+    
+    // Restore file permissions
+    if (chmod(output_file, file_mode) != 0) {
+        printf("Warning: Cannot restore file permissions\n");
+    }
+    
+    printf("File decrypted successfully: %s\n", output_file);
+    printf("Restored permissions and metadata\n");
+    
+    // Cleanup
+    free(encrypted_data);
+    free(pad_data);
+    
+    return 0;
+}
+
+int decrypt_ascii_file(const char* input_file, const char* output_file) {
+    FILE* input_fp = fopen(input_file, "r");
+    if (!input_fp) {
+        printf("Error: Cannot open input file %s\n", input_file);
+        return 1;
+    }
+    
+    // Read the entire ASCII armored content
+    char line[MAX_LINE_LENGTH];
+    char stored_chksum[MAX_HASH_LENGTH];
+    uint64_t pad_offset;
+    char base64_data[MAX_INPUT_SIZE * 8] = {0}; // Larger buffer for files
+    int in_data_section = 0;
+    int found_begin = 0;
+    
+    while (fgets(line, sizeof(line), input_fp)) {
+        line[strcspn(line, "\n\r")] = 0; // Remove newlines
+        
+        if (strcmp(line, "-----BEGIN OTP MESSAGE-----") == 0) {
+            found_begin = 1;
+            continue;
+        }
+        
+        if (strcmp(line, "-----END OTP MESSAGE-----") == 0) {
+            break;
+        }
+        
+        if (!found_begin) continue;
+        
+        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);
+        }
+        else if (strlen(line) == 0) {
+            in_data_section = 1;
+        }
+        else if (in_data_section) {
+            strncat(base64_data, line, sizeof(base64_data) - strlen(base64_data) - 1);
+        }
+    }
+    fclose(input_fp);
+    
+    if (!found_begin) {
+        printf("Error: Invalid ASCII armored format\n");
+        return 1;
+    }
+    
+    printf("Decrypting ASCII armored file...\n");
+    
+    // Check if we have the required pad
+    char pad_path[MAX_HASH_LENGTH + 20];
+    char state_path[MAX_HASH_LENGTH + 20];
+    get_pad_path(stored_chksum, pad_path, state_path);
+    
+    if (access(pad_path, R_OK) != 0) {
+        printf("Error: Required pad not found: %s\n", stored_chksum);
+        printf("Available pads:\n");
+        list_available_pads();
+        return 1;
+    }
+    
+    // Decode base64
+    int ciphertext_len;
+    unsigned char* ciphertext = custom_base64_decode(base64_data, &ciphertext_len);
+    if (!ciphertext) {
+        printf("Error: Invalid base64 data\n");
+        return 1;
+    }
+    
+    // Determine output filename
+    char default_output[512];
+    if (output_file == NULL) {
+        // Remove .otp.asc extension if present
+        strncpy(default_output, input_file, sizeof(default_output) - 1);
+        default_output[sizeof(default_output) - 1] = '\0';
+        
+        char* ext = strstr(default_output, ".otp.asc");
+        if (ext) {
+            *ext = '\0';
+        } else {
+            // Just add .decrypted suffix
+            strncat(default_output, ".decrypted", sizeof(default_output) - strlen(default_output) - 1);
+        }
+        output_file = default_output;
+    }
+    
+    // Open pad file and decrypt
+    FILE* pad_file = fopen(pad_path, "rb");
+    if (!pad_file) {
+        printf("Error: Cannot open pad file\n");
+        free(ciphertext);
+        return 1;
+    }
+    
+    if (fseek(pad_file, pad_offset, SEEK_SET) != 0) {
+        printf("Error: Cannot seek to offset in pad file\n");
+        free(ciphertext);
+        fclose(pad_file);
+        return 1;
+    }
+    
+    unsigned char* pad_data = malloc(ciphertext_len);
+    if (fread(pad_data, 1, ciphertext_len, pad_file) != (size_t)ciphertext_len) {
+        printf("Error: Cannot read pad data\n");
+        free(ciphertext);
+        free(pad_data);
+        fclose(pad_file);
+        return 1;
+    }
+    fclose(pad_file);
+    
+    // XOR decrypt
+    for (int i = 0; i < ciphertext_len; i++) {
+        ciphertext[i] ^= pad_data[i];
+    }
+    
+    // Write decrypted file
+    FILE* output_fp = fopen(output_file, "wb");
+    if (!output_fp) {
+        printf("Error: Cannot create output file %s\n", output_file);
+        free(ciphertext);
+        free(pad_data);
+        return 1;
+    }
+    
+    if (fwrite(ciphertext, 1, ciphertext_len, output_fp) != (size_t)ciphertext_len) {
+        printf("Error: Cannot write decrypted data\n");
+        free(ciphertext);
+        free(pad_data);
+        fclose(output_fp);
+        return 1;
+    }
+    fclose(output_fp);
+    
+    printf("File decrypted successfully: %s\n", output_file);
+    printf("Note: ASCII format does not preserve original filename/permissions\n");
+    
+    // Cleanup
+    free(ciphertext);
+    free(pad_data);
+    
+    return 0;
+}
+
 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_chksum);
@@ -1395,16 +2054,27 @@ void print_usage(const char* program_name) {
     printf("OTP Cipher - One Time Pad Implementation %s\n", get_version());
     printf("%s\n", get_build_info());
     printf("Usage:\n");
-    printf("  %s                                        - Interactive mode\n", program_name);
+    printf("  %s                                         - Interactive mode\n", program_name);
-    printf("  %s generate <size>                        - Generate new pad\n", program_name);
+    printf("  %s generate|-g <size>                      - Generate new pad\n", program_name);
-    printf("  %s encrypt <pad_checksum_prefix> [text]   - Encrypt text\n", program_name);
+    printf("  %s encrypt|-e <pad_checksum_prefix> [text] - Encrypt text\n", program_name);
-    printf("  %s decrypt <pad_checksum_prefix> [message] - Decrypt message\n", program_name);
+    printf("  %s decrypt|-d [encrypted_message]          - Decrypt message\n", program_name);
-    printf("  %s list                                   - List available pads\n", program_name);
+    printf("  %s -f <file> <pad_prefix> [-a] [-o <out>]  - Encrypt file\n", program_name);
+    printf("  %s list|-l                                 - List available pads\n", program_name);
+    printf("\nFile Operations:\n");
+    printf("  -f <file> <pad>     - Encrypt file (binary .otp format)\n");
+    printf("  -f <file> <pad> -a  - Encrypt file (ASCII .otp.asc format)\n");
+    printf("  -o <output>         - Specify output filename\n");
+    printf("\nShort flags:\n");
+    printf("  -g generate   -e encrypt   -d decrypt   -l list   -f file\n");
     printf("\nExamples:\n");
-    printf("  %s encrypt 1a2b3c \"Hello world\"          - Encrypt inline text\n", program_name);
+    printf("  %s -e 1a2b3c \"Hello world\"                  - Encrypt inline text\n", program_name);
-    printf("  %s encrypt 1a2b3c                        - Encrypt interactively\n", program_name);
+    printf("  %s -f document.pdf 1a2b                     - Encrypt file (binary)\n", program_name);
-    printf("  %s decrypt 1a2b3c \"-----BEGIN OTP...\"     - Decrypt inline message\n", program_name);
+    printf("  %s -f document.pdf 1a2b -a                  - Encrypt file (ASCII)\n", program_name);
-    printf("  %s decrypt 1a2b3c                        - Decrypt interactively\n", program_name);
+    printf("  %s -f document.pdf 1a2b -o secret.otp       - Encrypt with custom output\n", program_name);
+    printf("  %s -d \"-----BEGIN OTP MESSAGE-----...\"      - Decrypt message/file\n", program_name);
+    printf("  %s -d encrypted.otp.asc                     - Decrypt ASCII file\n", program_name);
+    printf("  %s -g 1GB                                   - Generate 1GB pad\n", program_name);
+    printf("  %s -l                                       - List pads\n", program_name);
     printf("\nSize examples: 1GB, 5TB, 512MB, 2048 (bytes)\n");
     printf("Pad selection: Full chksum, prefix, or number from list\n");
 }

test.txt

@@ -0,0 +1 @@
+This is a test file for OTP encryption.

test_ascii

@@ -0,0 +1 @@
+This is a test file for OTP encryption.

test_ascii.otp.asc

@@ -0,0 +1,7 @@
+-----BEGIN OTP MESSAGE-----
+Version: v0.2.15
+Pad-ChkSum: 0c8e19fde996e683fdbd348d1052eec168ffe6f67a88bb1278d0d02e9341b87b
+Pad-Offset: 210
+
+mMIm7iVtUO6NbXbskMxtydI/A16UXEQUGTcIya/8Dja6PB3EC0MLdw==
+-----END OTP MESSAGE-----