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Added exponential padding to increase security.

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This commit is contained in:
Laan Tungir
2026-01-13 03:13:54 -05:00
parent 302b200548
commit 2e2f78720e
6 changed files with 459 additions and 97 deletions
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25
README.md
View File

@@ -43,6 +43,7 @@ One-time pads can be trivially encrypted and decrypted using pencil and paper, m
## Features ## Features
- **Perfect Security**: Implements true one-time pad encryption with information-theoretic security - **Perfect Security**: Implements true one-time pad encryption with information-theoretic security
- **Traffic Analysis Resistance**: Exponential bucketing with ISO/IEC 9797-1 Method 2 (Padmé) padding hides message lengths
- **Text & File Encryption**: Supports both inline text and file encryption - **Text & File Encryption**: Supports both inline text and file encryption
- **Multiple Output Formats**: Binary (.otp) and ASCII armored (.otp.asc) file formats - **Multiple Output Formats**: Binary (.otp) and ASCII armored (.otp.asc) file formats
- **Hardware RNG Support**: Direct entropy collection from TrueRNG USB devices with automatic detection - **Hardware RNG Support**: Direct entropy collection from TrueRNG USB devices with automatic detection
@@ -58,14 +59,14 @@ One-time pads can be trivially encrypted and decrypted using pencil and paper, m
### Download Pre-Built Binaries ### Download Pre-Built Binaries
**[Download Current Linux x86](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.47/otp-v0.3.47-linux-x86_64)** **[Download Current Linux x86](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.48/otp-v0.3.48-linux-x86_64)**
**[Download Current Raspberry Pi 64](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.47/otp-v0.3.47-linux-arm64)** **[Download Current Raspberry Pi 64](https://git.laantungir.net/laantungir/otp/releases/download/v0.3.48/otp-v0.3.48-linux-arm64)**
After downloading: After downloading:
```bash ```bash
# Rename for convenience, then make executable # Rename for convenience, then make executable
mv otp-v0.3.47-linux-x86_64 otp mv otp-v0.3.48-linux-x86_64 otp
chmod +x otp chmod +x otp
# Run it # Run it
@@ -189,8 +190,23 @@ git tag v1.0.0 # Next build: v1.0.1
- Custom 256-bit XOR checksum for pad identification (encrypted with pad data) - Custom 256-bit XOR checksum for pad identification (encrypted with pad data)
- Read-only pad files to prevent accidental modification - Read-only pad files to prevent accidental modification
- State tracking to prevent pad reuse - State tracking to prevent pad reuse
- **Message Length Hiding**: Exponential bucketing (256B, 512B, 1KB, 2KB, 4KB...) prevents traffic analysis
- **ISO/IEC 9797-1 Method 2 Padding**: Standard-compliant Padmé padding with 0x80 marker
- **Zero external crypto dependencies** - completely self-contained implementation - **Zero external crypto dependencies** - completely self-contained implementation
### Message Padding
All encrypted messages and files are automatically padded using exponential bucketing to resist traffic analysis attacks:
- **Minimum size**: 256 bytes
- **Bucket sizes**: 256B → 512B → 1KB → 2KB → 4KB → 8KB → ...
- **Padding method**: ISO/IEC 9797-1 Method 2 (Padmé padding)
- Appends `0x80` byte after message
- Fills remaining space with `0x00` bytes
- Unambiguous padding removal during decryption
**Example**: A 10-byte message is padded to 256 bytes, while a 300-byte message is padded to 512 bytes. This provides strong protection for small messages where length leakage matters most, with logarithmic overhead for larger messages.
## Project Structure ## Project Structure
``` ```
@@ -205,6 +221,7 @@ otp/
│ ├── ui.c # Interactive user interface and menu system │ ├── ui.c # Interactive user interface and menu system
│ ├── state.c # Global state management (pads directory, preferences) │ ├── state.c # Global state management (pads directory, preferences)
│ ├── crypto.c # Core cryptographic operations (XOR, base64) │ ├── crypto.c # Core cryptographic operations (XOR, base64)
│ ├── padding.c # Message padding (exponential bucketing, Padmé padding)
│ ├── pads.c # Pad management and file operations │ ├── pads.c # Pad management and file operations
│ ├── entropy.c # Entropy collection from various sources │ ├── entropy.c # Entropy collection from various sources
│ ├── trng.c # Hardware RNG device detection and collection │ ├── trng.c # Hardware RNG device detection and collection
@@ -217,6 +234,7 @@ otp/
├── pads/ # OTP pad storage directory (created at runtime) ├── pads/ # OTP pad storage directory (created at runtime)
├── files/ # Encrypted file storage (created at runtime) ├── files/ # Encrypted file storage (created at runtime)
└── tests/ # Test scripts and utilities └── tests/ # Test scripts and utilities
└── test_padding.sh # Padding implementation tests
``` ```
## Architecture ## Architecture
@@ -227,6 +245,7 @@ The OTP cipher uses a modular architecture with clean separation of concerns:
- **ui.c**: Interactive user interface, menus, and terminal management - **ui.c**: Interactive user interface, menus, and terminal management
- **state.c**: Global state management (pads directory, terminal dimensions, preferences) - **state.c**: Global state management (pads directory, terminal dimensions, preferences)
- **crypto.c**: Core cryptographic operations (XOR encryption, base64 encoding) - **crypto.c**: Core cryptographic operations (XOR encryption, base64 encoding)
- **padding.c**: Message padding implementation (exponential bucketing, ISO/IEC 9797-1 Method 2)
- **pads.c**: Pad file management, checksums, and state tracking - **pads.c**: Pad file management, checksums, and state tracking
- **entropy.c**: Entropy collection from keyboard, dice, files, and hardware RNG - **entropy.c**: Entropy collection from keyboard, dice, files, and hardware RNG
- **trng.c**: Hardware RNG device detection and entropy collection from USB devices - **trng.c**: Hardware RNG device detection and entropy collection from USB devices

13
src/archive.c
View File

@@ -476,7 +476,18 @@ int decrypt_and_extract_directory(const char* encrypted_file, const char* output
unlink(temp_decrypted); unlink(temp_decrypted);
} else { } else {
// Not compressed, assume it's already TAR // Not compressed, assume it's already TAR
rename(temp_decrypted, temp_tar); printf("File is not compressed, using as TAR directly...\n");
if (rename(temp_decrypted, temp_tar) != 0) {
printf("Error: Failed to rename decrypted file to TAR file\n");
unlink(temp_decrypted);
return 1;
}
}
// Verify TAR file exists before extraction
if (access(temp_tar, F_OK) != 0) {
printf("Error: TAR file does not exist at '%s'\n", temp_tar);
return 1;
} }
printf("Extracting archive...\n"); printf("Extracting archive...\n");

285
src/crypto.c
View File

@@ -401,18 +401,40 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
return 1; return 1;
} }
// Check if we have enough pad space // Calculate chunk size for padding (exponential bucketing)
struct stat pad_stat; size_t chunk_size = calculate_chunk_size(input_len);
if (stat(pad_path, &pad_stat) != 0) {
printf("Error: Cannot get pad file size\n"); // Allocate buffer for padded message
unsigned char* padded_buffer = malloc(chunk_size);
if (!padded_buffer) {
printf("Error: Memory allocation failed\n");
free(pad_chksum);
return 1;
}
// Copy message to buffer and apply padding
memcpy(padded_buffer, text_buffer, input_len);
if (apply_padme_padding(padded_buffer, input_len, chunk_size) != 0) {
printf("Error: Failed to apply padding\n");
free(padded_buffer);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
if (current_offset + input_len > (uint64_t)pad_stat.st_size) { // Check if we have enough pad space (now using chunk_size instead of input_len)
struct stat pad_stat;
if (stat(pad_path, &pad_stat) != 0) {
printf("Error: Cannot get pad file size\n");
free(padded_buffer);
free(pad_chksum);
return 1;
}
if (current_offset + chunk_size > (uint64_t)pad_stat.st_size) {
printf("Error: Not enough pad space remaining\n"); printf("Error: Not enough pad space remaining\n");
printf("Need: %lu bytes, Available: %lu bytes\n", printf("Need: %lu bytes, Available: %lu bytes\n",
input_len, (uint64_t)pad_stat.st_size - current_offset); chunk_size, (uint64_t)pad_stat.st_size - current_offset);
free(padded_buffer);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
@@ -432,37 +454,40 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
return 1; return 1;
} }
unsigned char* pad_data = malloc(input_len); unsigned char* pad_data = malloc(chunk_size);
if (fread(pad_data, 1, input_len, pad_file) != input_len) { if (fread(pad_data, 1, chunk_size, pad_file) != chunk_size) {
printf("Error: Cannot read pad data\n"); printf("Error: Cannot read pad data\n");
free(pad_data); free(pad_data);
fclose(pad_file); fclose(pad_file);
free(padded_buffer);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
fclose(pad_file); fclose(pad_file);
// Use universal XOR operation for encryption // Use universal XOR operation for encryption (now with padded data)
unsigned char* ciphertext = malloc(input_len); unsigned char* ciphertext = malloc(chunk_size);
if (universal_xor_operation((const unsigned char*)text_buffer, input_len, pad_data, ciphertext) != 0) { if (universal_xor_operation(padded_buffer, chunk_size, pad_data, ciphertext) != 0) {
printf("Error: Encryption operation failed\n"); printf("Error: Encryption operation failed\n");
free(pad_data); free(pad_data);
free(ciphertext); free(ciphertext);
free(padded_buffer);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
// Update state offset // Update state offset (now using chunk_size)
if (write_state_offset(pad_chksum, current_offset + input_len) != 0) { if (write_state_offset(pad_chksum, current_offset + chunk_size) != 0) {
printf("Warning: Failed to update state file\n"); printf("Warning: Failed to update state file\n");
} }
// Use universal ASCII armor generator // Use universal ASCII armor generator (now with chunk_size)
char* ascii_output; char* ascii_output;
if (generate_ascii_armor(pad_chksum, current_offset, ciphertext, input_len, &ascii_output) != 0) { if (generate_ascii_armor(pad_chksum, current_offset, ciphertext, chunk_size, &ascii_output) != 0) {
printf("Error: Failed to generate ASCII armor\n"); printf("Error: Failed to generate ASCII armor\n");
free(pad_data); free(pad_data);
free(ciphertext); free(ciphertext);
free(padded_buffer);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
@@ -479,6 +504,7 @@ int encrypt_text(const char* pad_identifier, const char* input_text) {
// Cleanup // Cleanup
free(pad_data); free(pad_data);
free(ciphertext); free(ciphertext);
free(padded_buffer);
free(ascii_output); free(ascii_output);
free(pad_chksum); free(pad_chksum);
@@ -632,6 +658,22 @@ int universal_decrypt(const char* input_data, const char* output_target, decrypt
return 1; return 1;
} }
// Remove padding to get actual message
size_t actual_msg_len;
if (remove_padme_padding(ciphertext, ciphertext_len, &actual_msg_len) != 0) {
if (mode == DECRYPT_MODE_SILENT) {
fprintf(stderr, "Error: Invalid padding - message may be corrupted\n");
} else {
printf("Error: Invalid padding - message may be corrupted\n");
}
free(ciphertext);
free(pad_data);
return 1;
}
// Update ciphertext_len to actual message length
ciphertext_len = actual_msg_len;
// Output based on mode // Output based on mode
if (mode == DECRYPT_MODE_FILE_TO_FILE) { if (mode == DECRYPT_MODE_FILE_TO_FILE) {
// Write to output file // Write to output file
@@ -740,6 +782,9 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
return 1; return 1;
} }
// Calculate chunk size for padding (exponential bucketing)
size_t chunk_size = calculate_chunk_size(file_size);
// Check if pad file exists // Check if pad file exists
if (access(pad_path, R_OK) != 0) { if (access(pad_path, R_OK) != 0) {
printf("Error: Pad file %s not found\n", pad_path); printf("Error: Pad file %s not found\n", pad_path);
@@ -774,10 +819,10 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
return 1; return 1;
} }
if (current_offset + file_size > (uint64_t)pad_stat.st_size) { if (current_offset + chunk_size > (uint64_t)pad_stat.st_size) {
printf("Error: Not enough pad space remaining\n"); printf("Error: Not enough pad space remaining\n");
printf("Need: %lu bytes, Available: %lu bytes\n", printf("Need: %lu bytes (file: %lu + padding), Available: %lu bytes\n",
file_size, (uint64_t)pad_stat.st_size - current_offset); chunk_size, file_size, (uint64_t)pad_stat.st_size - current_offset);
free(pad_chksum); free(pad_chksum);
return 1; return 1;
} }
@@ -822,66 +867,93 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
return 1; return 1;
} }
// Read and encrypt file // Allocate buffer for padded file data
unsigned char buffer[64 * 1024]; unsigned char* file_data = malloc(file_size);
unsigned char pad_buffer[64 * 1024]; if (!file_data) {
unsigned char* encrypted_data = malloc(file_size); printf("Error: Memory allocation failed\n");
uint64_t bytes_processed = 0; fclose(input_fp);
fclose(pad_file);
free(pad_chksum);
return 1;
}
printf("Encrypting %s...\n", input_file); printf("Encrypting %s...\n", input_file);
while (bytes_processed < file_size) { // Read entire file
uint64_t chunk_size = sizeof(buffer); if (fread(file_data, 1, file_size, input_fp) != file_size) {
if (file_size - bytes_processed < chunk_size) { printf("Error: Cannot read input file\n");
chunk_size = file_size - bytes_processed; free(file_data);
} fclose(input_fp);
fclose(pad_file);
// Read file data free(pad_chksum);
if (fread(buffer, 1, chunk_size, input_fp) != chunk_size) { return 1;
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;
}
// Use universal XOR operation for encryption
if (universal_xor_operation(buffer, chunk_size, pad_buffer, &encrypted_data[bytes_processed]) != 0) {
printf("Error: Encryption operation failed\n");
free(encrypted_data);
fclose(input_fp);
fclose(pad_file);
free(pad_chksum);
return 1;
}
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); // MOVED TO src/util.c
}
} }
if (file_size > 10 * 1024 * 1024) {
// show_progress(file_size, file_size, start_time); // MOVED TO src/util.c
printf("\n");
}
fclose(input_fp); fclose(input_fp);
// Allocate buffer for padded data
unsigned char* padded_data = malloc(chunk_size);
if (!padded_data) {
printf("Error: Memory allocation failed\n");
free(file_data);
fclose(pad_file);
free(pad_chksum);
return 1;
}
// Copy file data and apply padding
memcpy(padded_data, file_data, file_size);
free(file_data);
if (apply_padme_padding(padded_data, file_size, chunk_size) != 0) {
printf("Error: Failed to apply padding\n");
free(padded_data);
fclose(pad_file);
free(pad_chksum);
return 1;
}
// Read pad data
unsigned char* pad_data = malloc(chunk_size);
if (!pad_data) {
printf("Error: Memory allocation failed\n");
free(padded_data);
fclose(pad_file);
free(pad_chksum);
return 1;
}
if (fread(pad_data, 1, chunk_size, pad_file) != chunk_size) {
printf("Error: Cannot read pad data\n");
free(padded_data);
free(pad_data);
fclose(pad_file);
free(pad_chksum);
return 1;
}
fclose(pad_file); fclose(pad_file);
// Encrypt padded data
unsigned char* encrypted_data = malloc(chunk_size);
if (!encrypted_data) {
printf("Error: Memory allocation failed\n");
free(padded_data);
free(pad_data);
free(pad_chksum);
return 1;
}
if (universal_xor_operation(padded_data, chunk_size, pad_data, encrypted_data) != 0) {
printf("Error: Encryption operation failed\n");
free(padded_data);
free(pad_data);
free(encrypted_data);
free(pad_chksum);
return 1;
}
free(padded_data);
free(pad_data);
// Write output file // Write output file
if (ascii_armor) { if (ascii_armor) {
// ASCII armored format - same as message format // ASCII armored format - same as message format
@@ -893,9 +965,9 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
return 1; return 1;
} }
// Use universal ASCII armor generator // Use universal ASCII armor generator (now with chunk_size)
char* ascii_output; char* ascii_output;
if (generate_ascii_armor(pad_chksum, current_offset, encrypted_data, file_size, &ascii_output) != 0) { if (generate_ascii_armor(pad_chksum, current_offset, encrypted_data, chunk_size, &ascii_output) != 0) {
printf("Error: Failed to generate ASCII armor\n"); printf("Error: Failed to generate ASCII armor\n");
fclose(output_fp); fclose(output_fp);
free(encrypted_data); free(encrypted_data);
@@ -941,17 +1013,17 @@ int encrypt_file(const char* pad_identifier, const char* input_file, const char*
uint32_t file_mode = input_stat.st_mode; uint32_t file_mode = input_stat.st_mode;
fwrite(&file_mode, sizeof(uint32_t), 1, output_fp); fwrite(&file_mode, sizeof(uint32_t), 1, output_fp);
// File size: 8 bytes // File size: 8 bytes (original file size, not padded)
fwrite(&file_size, sizeof(uint64_t), 1, output_fp); fwrite(&file_size, sizeof(uint64_t), 1, output_fp);
// Encrypted data // Encrypted data (padded)
fwrite(encrypted_data, 1, file_size, output_fp); fwrite(encrypted_data, 1, chunk_size, output_fp);
fclose(output_fp); fclose(output_fp);
} }
// Update state offset // Update state offset (now using chunk_size)
if (write_state_offset(pad_chksum, current_offset + file_size) != 0) { if (write_state_offset(pad_chksum, current_offset + chunk_size) != 0) {
printf("Warning: Failed to update state file\n"); printf("Warning: Failed to update state file\n");
} }
@@ -1012,14 +1084,14 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
unsigned char pad_chksum_bin[32]; unsigned char pad_chksum_bin[32];
uint64_t pad_offset; uint64_t pad_offset;
uint32_t file_mode; uint32_t file_mode;
uint64_t file_size; uint64_t original_file_size;
if (fread(magic, 1, 4, input_fp) != 4 || if (fread(magic, 1, 4, input_fp) != 4 ||
fread(&version, sizeof(uint16_t), 1, input_fp) != 1 || fread(&version, sizeof(uint16_t), 1, input_fp) != 1 ||
fread(pad_chksum_bin, 1, 32, input_fp) != 32 || fread(pad_chksum_bin, 1, 32, input_fp) != 32 ||
fread(&pad_offset, sizeof(uint64_t), 1, input_fp) != 1 || fread(&pad_offset, sizeof(uint64_t), 1, input_fp) != 1 ||
fread(&file_mode, sizeof(uint32_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) { fread(&original_file_size, sizeof(uint64_t), 1, input_fp) != 1) {
printf("Error: Cannot read binary header\n"); printf("Error: Cannot read binary header\n");
fclose(input_fp); fclose(input_fp);
return 1; return 1;
@@ -1039,7 +1111,7 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
pad_chksum_hex[64] = '\0'; pad_chksum_hex[64] = '\0';
printf("Decrypting binary file...\n"); printf("Decrypting binary file...\n");
printf("File size: %lu bytes\n", file_size); printf("Original file size: %lu bytes\n", original_file_size);
// Check if we have the required pad // Check if we have the required pad
char pad_path[MAX_HASH_LENGTH + 20]; char pad_path[MAX_HASH_LENGTH + 20];
@@ -1064,9 +1136,18 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
output_file = default_output; output_file = default_output;
} }
// Read encrypted data // Calculate chunk size (encrypted data is padded)
unsigned char* encrypted_data = malloc(file_size); size_t chunk_size = calculate_chunk_size(original_file_size);
if (fread(encrypted_data, 1, file_size, input_fp) != file_size) {
// Read encrypted (padded) data
unsigned char* encrypted_data = malloc(chunk_size);
if (!encrypted_data) {
printf("Error: Memory allocation failed\n");
fclose(input_fp);
return 1;
}
if (fread(encrypted_data, 1, chunk_size, input_fp) != chunk_size) {
printf("Error: Cannot read encrypted data\n"); printf("Error: Cannot read encrypted data\n");
free(encrypted_data); free(encrypted_data);
fclose(input_fp); fclose(input_fp);
@@ -1089,8 +1170,15 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
return 1; return 1;
} }
unsigned char* pad_data = malloc(file_size); unsigned char* pad_data = malloc(chunk_size);
if (fread(pad_data, 1, file_size, pad_file) != file_size) { if (!pad_data) {
printf("Error: Memory allocation failed\n");
free(encrypted_data);
fclose(pad_file);
return 1;
}
if (fread(pad_data, 1, chunk_size, pad_file) != chunk_size) {
printf("Error: Cannot read pad data\n"); printf("Error: Cannot read pad data\n");
free(encrypted_data); free(encrypted_data);
free(pad_data); free(pad_data);
@@ -1100,26 +1188,40 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
fclose(pad_file); fclose(pad_file);
// Use universal XOR operation for decryption // Use universal XOR operation for decryption
if (universal_xor_operation(encrypted_data, file_size, pad_data, encrypted_data) != 0) { if (universal_xor_operation(encrypted_data, chunk_size, pad_data, encrypted_data) != 0) {
printf("Error: Decryption operation failed\n"); printf("Error: Decryption operation failed\n");
free(encrypted_data); free(encrypted_data);
free(pad_data); free(pad_data);
return 1; return 1;
} }
// Write decrypted file free(pad_data);
// Remove padding to get original file
size_t actual_file_size;
if (remove_padme_padding(encrypted_data, chunk_size, &actual_file_size) != 0) {
printf("Error: Invalid padding - file may be corrupted\n");
free(encrypted_data);
return 1;
}
// Verify the actual size matches the stored original size
if (actual_file_size != original_file_size) {
printf("Warning: Decrypted size (%lu) doesn't match stored size (%lu)\n",
actual_file_size, original_file_size);
}
// Write decrypted file (using actual_file_size)
FILE* output_fp = fopen(output_file, "wb"); FILE* output_fp = fopen(output_file, "wb");
if (!output_fp) { if (!output_fp) {
printf("Error: Cannot create output file %s\n", output_file); printf("Error: Cannot create output file %s\n", output_file);
free(encrypted_data); free(encrypted_data);
free(pad_data);
return 1; return 1;
} }
if (fwrite(encrypted_data, 1, file_size, output_fp) != file_size) { if (fwrite(encrypted_data, 1, actual_file_size, output_fp) != actual_file_size) {
printf("Error: Cannot write decrypted data\n"); printf("Error: Cannot write decrypted data\n");
free(encrypted_data); free(encrypted_data);
free(pad_data);
fclose(output_fp); fclose(output_fp);
return 1; return 1;
} }
@@ -1141,7 +1243,6 @@ int decrypt_binary_file(FILE* input_fp, const char* output_file) {
// Cleanup // Cleanup
free(encrypted_data); free(encrypted_data);
free(pad_data);
return 0; return 0;
} }

12
src/main.h
View File

@@ -23,7 +23,7 @@
#include <ctype.h> #include <ctype.h>
// Version - Updated automatically by build.sh // Version - Updated automatically by build.sh
#define OTP_VERSION "v0.3.47" #define OTP_VERSION "v0.3.48"
// Constants // Constants
#define MAX_INPUT_SIZE 4096 #define MAX_INPUT_SIZE 4096
@@ -267,6 +267,16 @@ const char* get_files_directory(void);
void get_default_file_path(const char* filename, char* result_path, size_t result_size); void get_default_file_path(const char* filename, char* result_path, size_t result_size);
void get_directory_display(const char* file_path, char* result, size_t result_size); void get_directory_display(const char* file_path, char* result, size_t result_size);
////////////////////////////////////////////////////////////////////////////////
// MESSAGE PADDING FUNCTIONS
////////////////////////////////////////////////////////////////////////////////
// Exponential bucketing and ISO/IEC 9797-1 Method 2 (Padmé) padding
size_t calculate_chunk_size(size_t msg_len);
int apply_padme_padding(unsigned char* buffer, size_t msg_len, size_t chunk_size);
int remove_padme_padding(const unsigned char* buffer, size_t chunk_size, size_t* msg_len);
void format_chunk_size(size_t chunk_size, char* buffer, size_t buffer_size);
//////////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////////////
// UTILITY FUNCTIONS // UTILITY FUNCTIONS
//////////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////////////

92
src/padding.c Normal file
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@@ -0,0 +1,92 @@
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include "main.h"
////////////////////////////////////////////////////////////////////////////////
// MESSAGE PADDING IMPLEMENTATION
// ISO/IEC 9797-1 Method 2 (Padmé Padding)
// with Exponential Bucketing for Traffic Analysis Resistance
////////////////////////////////////////////////////////////////////////////////
// Calculate required chunk size using exponential bucketing
// Starting at 256 bytes, doubling each time
// Provides strong protection against length analysis attacks
size_t calculate_chunk_size(size_t msg_len) {
size_t chunk = 256; // Minimum chunk size: 256 bytes
// Need space for message + 0x80 byte (minimum 1 byte padding)
while (chunk < msg_len + 1) {
chunk *= 2;
}
return chunk;
}
// Apply ISO/IEC 9797-1 Method 2 (Padmé) padding
// Appends 0x80 byte followed by 0x00 bytes to reach chunk boundary
// Returns 0 on success, non-zero on error
int apply_padme_padding(unsigned char* buffer, size_t msg_len, size_t chunk_size) {
if (!buffer) {
return 1; // Error: null pointer
}
if (chunk_size < msg_len + 1) {
return 2; // Error: chunk size too small for message + padding
}
// Apply padding: 0x80 followed by 0x00 bytes
buffer[msg_len] = 0x80;
// Fill remaining bytes with 0x00
if (chunk_size > msg_len + 1) {
memset(buffer + msg_len + 1, 0x00, chunk_size - msg_len - 1);
}
return 0; // Success
}
// Remove ISO/IEC 9797-1 Method 2 (Padmé) padding
// Scans backwards for 0x80 marker, validates padding
// Returns 0 on success, non-zero on error
// Sets msg_len to the actual message length (excluding padding)
int remove_padme_padding(const unsigned char* buffer, size_t chunk_size, size_t* msg_len) {
if (!buffer || !msg_len) {
return 1; // Error: null pointer
}
if (chunk_size == 0) {
return 2; // Error: invalid chunk size
}
// Scan backwards from end to find 0x80 marker
for (int i = chunk_size - 1; i >= 0; i--) {
if (buffer[i] == 0x80) {
// Found the padding marker
*msg_len = i;
return 0; // Success
} else if (buffer[i] != 0x00) {
// Found non-zero, non-0x80 byte - invalid padding
return 3; // Error: invalid padding (corrupted or tampered data)
}
}
// No 0x80 marker found - invalid padding
return 4; // Error: no padding marker found
}
// Helper function to get human-readable chunk size
// Useful for debugging and user feedback
void format_chunk_size(size_t chunk_size, char* buffer, size_t buffer_size) {
if (!buffer || buffer_size == 0) return;
if (chunk_size < 1024) {
snprintf(buffer, buffer_size, "%zu bytes", chunk_size);
} else if (chunk_size < 1024 * 1024) {
snprintf(buffer, buffer_size, "%.1f KB", chunk_size / 1024.0);
} else if (chunk_size < 1024 * 1024 * 1024) {
snprintf(buffer, buffer_size, "%.1f MB", chunk_size / (1024.0 * 1024.0));
} else {
snprintf(buffer, buffer_size, "%.1f GB", chunk_size / (1024.0 * 1024.0 * 1024.0));
}
}

129
tests/test_padding.sh Executable file
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@@ -0,0 +1,129 @@
#!/bin/bash
# Test script for message padding implementation
set -e
echo "=== Testing Message Padding Implementation ==="
echo ""
# Colors
GREEN='\033[0;32m'
RED='\033[0;31m'
NC='\033[0m' # No Color
# Test counter
TESTS_PASSED=0
TESTS_FAILED=0
# Function to run a test
run_test() {
local test_name="$1"
local test_command="$2"
echo -n "Testing: $test_name... "
if eval "$test_command" > /dev/null 2>&1; then
echo -e "${GREEN}PASS${NC}"
((TESTS_PASSED++))
return 0
else
echo -e "${RED}FAIL${NC}"
((TESTS_FAILED++))
return 1
fi
}
# Create a small test pad if it doesn't exist
if [ ! -f "pads/"*.pad ]; then
echo "Creating test pad (1MB)..."
./build/otp-x86_64 generate 1MB
echo ""
fi
# Get the first pad checksum
PAD_CHKSUM=$(ls pads/*.pad | head -n 1 | xargs basename | sed 's/.pad$//')
echo "Using pad: ${PAD_CHKSUM:0:16}..."
echo ""
# Test 1: Encrypt and decrypt a short message (should be padded to 256 bytes)
echo "Test 1: Short message (10 bytes -> 256 bytes padded)"
TEST_MSG="Hello Test"
ENCRYPTED=$(echo "$TEST_MSG" | ./build/otp-x86_64 encrypt ${PAD_CHKSUM:0:8})
DECRYPTED=$(echo "$ENCRYPTED" | ./build/otp-x86_64 decrypt)
if [ "$DECRYPTED" = "$TEST_MSG" ]; then
echo -e "${GREEN}✓ Short message encryption/decryption successful${NC}"
((TESTS_PASSED++))
else
echo -e "${RED}✗ Short message failed${NC}"
echo " Expected: $TEST_MSG"
echo " Got: $DECRYPTED"
((TESTS_FAILED++))
fi
echo ""
# Test 2: Encrypt and decrypt a medium message (should be padded to 512 bytes)
echo "Test 2: Medium message (~300 bytes -> 512 bytes padded)"
TEST_MSG=$(printf 'A%.0s' {1..300})
ENCRYPTED=$(echo "$TEST_MSG" | ./build/otp-x86_64 encrypt ${PAD_CHKSUM:0:8})
DECRYPTED=$(echo "$ENCRYPTED" | ./build/otp-x86_64 decrypt)
if [ "$DECRYPTED" = "$TEST_MSG" ]; then
echo -e "${GREEN}✓ Medium message encryption/decryption successful${NC}"
((TESTS_PASSED++))
else
echo -e "${RED}✗ Medium message failed${NC}"
((TESTS_FAILED++))
fi
echo ""
# Test 3: Encrypt and decrypt with special characters
echo "Test 3: Special characters and unicode"
TEST_MSG="Hello! @#$%^&*() 测试"
ENCRYPTED=$(echo "$TEST_MSG" | ./build/otp-x86_64 encrypt ${PAD_CHKSUM:0:8})
DECRYPTED=$(echo "$ENCRYPTED" | ./build/otp-x86_64 decrypt)
if [ "$DECRYPTED" = "$TEST_MSG" ]; then
echo -e "${GREEN}✓ Special characters encryption/decryption successful${NC}"
((TESTS_PASSED++))
else
echo -e "${RED}✗ Special characters failed${NC}"
echo " Expected: $TEST_MSG"
echo " Got: $DECRYPTED"
((TESTS_FAILED++))
fi
echo ""
# Test 4: File encryption/decryption with padding
echo "Test 4: File encryption/decryption"
TEST_FILE="/tmp/otp_test_file.txt"
echo "This is a test file for OTP encryption with padding." > "$TEST_FILE"
./build/otp-x86_64 -f "$TEST_FILE" ${PAD_CHKSUM:0:8} -a -o /tmp/test_encrypted.otp.asc
./build/otp-x86_64 decrypt /tmp/test_encrypted.otp.asc -o /tmp/test_decrypted.txt
if diff "$TEST_FILE" /tmp/test_decrypted.txt > /dev/null 2>&1; then
echo -e "${GREEN}✓ File encryption/decryption successful${NC}"
((TESTS_PASSED++))
else
echo -e "${RED}✗ File encryption/decryption failed${NC}"
((TESTS_FAILED++))
fi
# Cleanup
rm -f "$TEST_FILE" /tmp/test_encrypted.otp.asc /tmp/test_decrypted.txt
echo ""
# Summary
echo "=== Test Summary ==="
echo -e "Tests passed: ${GREEN}${TESTS_PASSED}${NC}"
echo -e "Tests failed: ${RED}${TESTS_FAILED}${NC}"
echo ""
if [ $TESTS_FAILED -eq 0 ]; then
echo -e "${GREEN}All tests passed!${NC}"
exit 0
else
echo -e "${RED}Some tests failed.${NC}"
exit 1
fi