Version v0.2.102 - Add entropy

.clinerules/workspace_rules.md

@@ -0,0 +1,29 @@
+When building, use build.sh, not make. 
+
+Use it as follows: build.sh -m "useful comment on changes being made"
+
+When making TUI menus, try to use the first leter of the command and the key to press to execute that command. For example, if the command is "Open file" try to use a keypress of "o" upper or lower case to signal to open the file. Use this instead of number keyed menus when possible. In the command, the letter should be underlined that signifies the command.
+
+## Buffer Size Guidelines
+
+### Path Handling
+- Always use buffers of size 1024 or PATH_MAX (4096) for file paths
+- When concatenating paths with snprintf, ensure buffer is at least 2x the expected maximum input
+- Use safer path construction patterns that check lengths before concatenation
+
+### String Formatting Safety
+- Before using snprintf with dynamic strings, validate that buffer size >= sum of all input string lengths + format characters + 1
+- Use strnlen() to check actual string lengths before formatting
+- Consider using asprintf() for dynamic allocation when exact size is unknown
+- Add length validation before snprintf calls
+
+### Compiler Warning Prevention
+- Always size string buffers generously (minimum 1024 for paths, 512 for general strings)
+- Use buffer size calculations: `size >= strlen(str1) + strlen(str2) + format_overhead + 1`
+- Add runtime length checks before snprintf operations
+- Consider using safer alternatives like strlcpy/strlcat if available
+
+### Code Patterns to Avoid
+- Fixed-size buffers (512 bytes) for path operations where inputs could be 255+ bytes each
+- Concatenating unchecked strings with snprintf
+- Assuming maximum path component sizes without validation

.gitignore

@@ -1,5 +1,7 @@
+otp
 pads/
 Gemini.md
+TropicOfCancer-HenryMiller.txt
 
 # Auto-generated version files
 src/version.h

Makefile

@@ -1,22 +1,21 @@
 CC = gcc
 CFLAGS = -Wall -Wextra -std=c99
-LIBS = 
-LIBS_STATIC = -static
+LIBS = -lm
+LIBS_STATIC = -static -lm
 TARGET = otp
 SOURCE = otp.c
-VERSION_SOURCE = src/version.c
+CHACHA20_SOURCE = nostr_chacha20.c
 
 # Default build target
 $(TARGET): $(SOURCE)
-	$(CC) $(CFLAGS) -o $(TARGET) $(SOURCE) $(VERSION_SOURCE) $(LIBS)
+	$(CC) $(CFLAGS) -o $(TARGET) $(SOURCE) $(CHACHA20_SOURCE) $(LIBS)
 
 # Static linking target
 static: $(SOURCE)
-	$(CC) $(CFLAGS) -o $(TARGET) $(SOURCE) $(VERSION_SOURCE) $(LIBS_STATIC)
+	$(CC) $(CFLAGS) -o $(TARGET) $(SOURCE) $(CHACHA20_SOURCE) $(LIBS_STATIC)
 
 clean:
 	rm -f $(TARGET) *.pad *.state
-	rm -f src/version.h src/version.c VERSION
 
 install:
 	sudo cp $(TARGET) /usr/local/bin/

README.md

@@ -1,24 +1,59 @@
-r# OTP Cipher - One Time Pad Implementation
+# OTP Cipher - One Time Pad Implementation
+
+
+## Introduction
+
+A secure one-time pad (OTP) cipher implementation in C.
+
+## Why One-Time Pads
+
+Nostr and much of the web runs on public key cryptography. Public key cryptography is great, but it is vulnerable. Cryptographers know this, and they know what it takes to attack it, so what they do is just make the keys large enough such that the system is resistant to attack given computers as they are today.
+
+There is one type of cryptography, however, that is invulnerable to any type of attack in our universe, and that is known as a one-time pad.
+
+One-time pads rely directly on the laws of physics and what it means for a number to be truly random.
+
+If you take your secret message and mix it with truly random numbers, and don't use those random numbers again, then that message is unbreakable by any computer, no matter how powerful, quantum or not, forever.
+
+In fact, one-time pads are so powerful that if you have data encrypted by a one-time pad located in a distant galaxy, and that data is not kept anywhere else, then by destroying the pad used for encryption in your galaxy, the data is wiped from the universe and can never be recovered.
+
+## Advantages and Limitations
+
+### Limitations
+
+1. The pad must be shared between the parties wanting to use it.
+2. The pad must be as long or longer than what you want to encrypt, and it can't be used a second time.
+
+### Modern Advantages
+
+While in the past, pad length might have been a problem, readily available USB drives in the terabytes make size less of a problem for many uses.
+
+We are also becoming very accustomed to YubiKey authenticators in the USB ports of our computers. A small USB drive in our devices can now easily contain a key of greater length than all the text messages we would expect to send over a lifetime.
+
+### Multi-Device Coordination
+
+One of the problems to address is the fact that to use an OTP across several devices means that they have to coordinate to know when they are encrypting new plaintext and where to start in the key. Reusing the same section of the pad, while not necessarily fatal, degrades the encryption from its status as "Information Theoretically Secure".
+
+To address this problem, we can use Nostr to share among devices the place in the pad that was last left off.
+
+### Additional Benefits
+
+One-time pads can be trivially encrypted and decrypted using pencil and paper, making them accessible even without electronic devices.
+
+
 
-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
 
-## Version Information
-
-This project uses an automatic versioning system that:
-- Automatically increments the patch version on each build
-- Embeds build timestamp, git commit hash, and branch information
-- Creates git tags for version tracking
-- Generates version header files with detailed build metadata
-
-Current version can be viewed with: `./otp --help` or by running the interactive mode.
 
 ## Building
 
@@ -28,7 +63,7 @@ Current version can be viewed with: `./otp --help` or by running the interactive
 - Git (for version tracking)
 - Make
 
-**Note: OpenSSL is no longer required! This implementation is now completely self-contained.**
+
 
 ### Build Commands
 
@@ -148,45 +183,122 @@ 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     | 4    | File Mode         | Original file permissions (uint32_t)
+50     | 8    | File Size         | Original file size (uint64_t)
+58     | 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 do not preserve original file permissions 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] New version: v0.1.5
-[SUCCESS] Created new version tag: v0.1.5
+[INFO] Current version: v0.2.14
+[INFO] New version: v0.2.15
+[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
-Built on 2025-08-10 at 08:17:47 from commit 9edfa5f on branch master
-Usage:
-  ./otp                              - Interactive mode
-  ...
+OTP Cipher - One Time Pad Implementation v0.2.15
+Built on 2025-08-10 at 14:07:58 from commit ae0afcf on branch master
 ```
 
-### Version History
+### Advanced Features
 ```bash
-$ git tag --list
-v0.1.0
-v0.1.1  
-v0.1.2
-v0.1.3
-v0.1.4
-v0.1.5
+# Generate pad with keyboard entropy
+./otp generate 5GB
+# Follow prompts for keyboard entropy collection
+
+# Check pad usage
+./otp -l
+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

TODO.md

@@ -0,0 +1,19 @@
+# TODO
+
+
+## Change technique for adding keyboard entropy.
+
+
+## There is the problem of the location of the pad revealing metadata about how many messages have been sent in the past, or at least the size of the messsages.
+
+One solution could be to start the pad at a random location, and then wrap around, so an attacker could never tell the size of the past text sent.  This helps. But then you have to store the start location, which you could do within the header of the pad along with the pad?
+
+Or, better yet, assume the offset is a very large size, and use the pad itself to encrypt the offset. 
+
+## Take a look at how the file header is being handled.
+
+
+## Setup for multiple USB drives
+
+
+

build.sh

@@ -13,6 +13,23 @@ print_success() { echo -e "${GREEN}[SUCCESS]${NC} $1"; }
 print_warning() { echo -e "${YELLOW}[WARNING]${NC} $1"; }
 print_error() { echo -e "${RED}[ERROR]${NC} $1"; }
 
+# Global variable for commit message
+COMMIT_MESSAGE=""
+
+# Parse command line arguments for -m flag
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        -m|--message)
+            COMMIT_MESSAGE="$2"
+            shift 2
+            ;;
+        *)
+            # Keep other arguments for main logic
+            break
+            ;;
+    esac
+done
+
 # Function to automatically increment version
 increment_version() {
     print_status "Incrementing version..."
@@ -57,8 +74,22 @@ increment_version() {
         print_warning "Failed to stage changes (maybe not a git repository)"
     fi
     
-    # Commit changes with version message
-    if git commit -m "Version $NEW_VERSION - Automatic version increment" 2>/dev/null; then
+    # Handle commit message - use global variable if set, otherwise prompt
+    if [[ -z "$COMMIT_MESSAGE" ]]; then
+        echo ""
+        print_status "Please enter a meaningful commit message for version $NEW_VERSION:"
+        echo -n "> "
+        read -r COMMIT_MESSAGE
+    fi
+    
+    # Check if user provided a message
+    if [[ -z "$COMMIT_MESSAGE" ]]; then
+        print_warning "No commit message provided. Using default message."
+        COMMIT_MESSAGE="Automatic version increment"
+    fi
+    
+    # Commit changes with user-provided message
+    if git commit -m "Version $NEW_VERSION - $COMMIT_MESSAGE" 2>/dev/null; then
         print_success "Committed changes for version $NEW_VERSION"
     else
         print_warning "Failed to commit changes (maybe no changes to commit or not a git repository)"
@@ -67,6 +98,19 @@ increment_version() {
     # Create new git tag
     if git tag "$NEW_VERSION" 2>/dev/null; then
         print_success "Created new version tag: $NEW_VERSION"
+        
+        # Push changes and tags to remote repository
+        if git push ssh://ubuntu@laantungir.net:/home/ubuntu/git_repos/otp 2>/dev/null; then
+            print_success "Pushed changes to remote repository"
+        else
+            print_warning "Failed to push changes to remote repository"
+        fi
+        
+        if git push ssh://ubuntu@laantungir.net:/home/ubuntu/git_repos/otp --tags 2>/dev/null; then
+            print_success "Pushed tags to remote repository"
+        else
+            print_warning "Failed to push tags to remote repository"
+        fi
     else
         print_warning "Tag $NEW_VERSION already exists - using existing version"
         NEW_VERSION=$LATEST_TAG
@@ -227,7 +271,10 @@ case "${1:-build}" in
         ;;
     *)
         echo "OTP Cipher Build Script"
-        echo "Usage: $0 {build|static|clean|install|uninstall|version}"
+        echo "Usage: $0 [-m \"commit message\"] {build|static|clean|install|uninstall|version}"
+        echo ""
+        echo "Options:"
+        echo "  -m, --message \"text\"  - Specify commit message (skips interactive prompt)"
         echo ""
         echo "Commands:"
         echo "  build     - Build project with automatic version increment (default)"
@@ -236,6 +283,11 @@ case "${1:-build}" in
         echo "  install   - Install to system (requires build first)"
         echo "  uninstall - Remove from system"
         echo "  version   - Generate version files only"
+        echo ""
+        echo "Examples:"
+        echo "  $0 build"
+        echo "  $0 -m \"Fixed checksum parsing bug\" build"
+        echo "  $0 --message \"Added new feature\" static"
         exit 1
         ;;
 esac

debug.c

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

files/o2.txt

@@ -0,0 +1 @@
+Hello, this is a test file for encryption!

files/test_decrypt.txt

@@ -0,0 +1 @@
+Test file content for decryption

files/test_file.txt

@@ -0,0 +1 @@
+Hello, this is a test file for encryption!

files/test_file.txt.otp.asc

@@ -0,0 +1,7 @@
+-----BEGIN OTP MESSAGE-----
+Version: v0.2.29
+Pad-ChkSum: d0d4a489354348b08d8c7b324814d8c50010042e9da47f2c973f32a16a09101b
+Pad-Offset: 57
+
+05S8GfS0tFfczNMUz0xrieFGoPSREM4uo5QhFGoBCcOzjfTXTDMt3hRtAQ==
+-----END OTP MESSAGE-----

files/test_input.txt

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

nostr_chacha20.c

@@ -0,0 +1,163 @@
+/*
+ * nostr_chacha20.c - ChaCha20 stream cipher implementation
+ * 
+ * Implementation based on RFC 8439 "ChaCha20 and Poly1305 for IETF Protocols"
+ * 
+ * This implementation is adapted from the RFC 8439 reference specification.
+ * It prioritizes correctness and clarity over performance optimization.
+ */
+
+#include "nostr_chacha20.h"
+#include <string.h>
+
+/*
+ * ============================================================================
+ * UTILITY MACROS AND FUNCTIONS
+ * ============================================================================
+ */
+
+/* Left rotate a 32-bit value by n bits */
+#define ROTLEFT(a, b) (((a) << (b)) | ((a) >> (32 - (b))))
+
+/* Convert 4 bytes to 32-bit little-endian */
+static uint32_t bytes_to_u32_le(const uint8_t *bytes) {
+    return ((uint32_t)bytes[0]) |
+           ((uint32_t)bytes[1] << 8) |
+           ((uint32_t)bytes[2] << 16) |
+           ((uint32_t)bytes[3] << 24);
+}
+
+/* Convert 32-bit to 4 bytes little-endian */
+static void u32_to_bytes_le(uint32_t val, uint8_t *bytes) {
+    bytes[0] = (uint8_t)(val & 0xff);
+    bytes[1] = (uint8_t)((val >> 8) & 0xff);
+    bytes[2] = (uint8_t)((val >> 16) & 0xff);
+    bytes[3] = (uint8_t)((val >> 24) & 0xff);
+}
+
+/*
+ * ============================================================================
+ * CHACHA20 CORE FUNCTIONS
+ * ============================================================================
+ */
+
+void chacha20_quarter_round(uint32_t state[16], int a, int b, int c, int d) {
+    state[a] += state[b]; 
+    state[d] ^= state[a]; 
+    state[d] = ROTLEFT(state[d], 16);
+    
+    state[c] += state[d]; 
+    state[b] ^= state[c]; 
+    state[b] = ROTLEFT(state[b], 12);
+    
+    state[a] += state[b]; 
+    state[d] ^= state[a]; 
+    state[d] = ROTLEFT(state[d], 8);
+    
+    state[c] += state[d]; 
+    state[b] ^= state[c]; 
+    state[b] = ROTLEFT(state[b], 7);
+}
+
+void chacha20_init_state(uint32_t state[16], const uint8_t key[32], 
+                         uint32_t counter, const uint8_t nonce[12]) {
+    /* ChaCha20 constants "expand 32-byte k" */
+    state[0] = 0x61707865;
+    state[1] = 0x3320646e;
+    state[2] = 0x79622d32;
+    state[3] = 0x6b206574;
+    
+    /* Key (8 words) */
+    state[4]  = bytes_to_u32_le(key + 0);
+    state[5]  = bytes_to_u32_le(key + 4);
+    state[6]  = bytes_to_u32_le(key + 8);
+    state[7]  = bytes_to_u32_le(key + 12);
+    state[8]  = bytes_to_u32_le(key + 16);
+    state[9]  = bytes_to_u32_le(key + 20);
+    state[10] = bytes_to_u32_le(key + 24);
+    state[11] = bytes_to_u32_le(key + 28);
+    
+    /* Counter (1 word) */
+    state[12] = counter;
+    
+    /* Nonce (3 words) */
+    state[13] = bytes_to_u32_le(nonce + 0);
+    state[14] = bytes_to_u32_le(nonce + 4);
+    state[15] = bytes_to_u32_le(nonce + 8);
+}
+
+void chacha20_serialize_state(const uint32_t state[16], uint8_t output[64]) {
+    for (int i = 0; i < 16; i++) {
+        u32_to_bytes_le(state[i], output + (i * 4));
+    }
+}
+
+int chacha20_block(const uint8_t key[32], uint32_t counter, 
+                   const uint8_t nonce[12], uint8_t output[64]) {
+    uint32_t state[16];
+    uint32_t initial_state[16];
+    
+    /* Initialize state */
+    chacha20_init_state(state, key, counter, nonce);
+    
+    /* Save initial state for later addition */
+    memcpy(initial_state, state, sizeof(initial_state));
+    
+    /* Perform 20 rounds (10 iterations of the 8 quarter rounds) */
+    for (int i = 0; i < 10; i++) {
+        /* Column rounds */
+        chacha20_quarter_round(state, 0, 4, 8,  12);
+        chacha20_quarter_round(state, 1, 5, 9,  13);
+        chacha20_quarter_round(state, 2, 6, 10, 14);
+        chacha20_quarter_round(state, 3, 7, 11, 15);
+        
+        /* Diagonal rounds */
+        chacha20_quarter_round(state, 0, 5, 10, 15);
+        chacha20_quarter_round(state, 1, 6, 11, 12);
+        chacha20_quarter_round(state, 2, 7, 8,  13);
+        chacha20_quarter_round(state, 3, 4, 9,  14);
+    }
+    
+    /* Add initial state back (prevents slide attacks) */
+    for (int i = 0; i < 16; i++) {
+        state[i] += initial_state[i];
+    }
+    
+    /* Serialize to output bytes */
+    chacha20_serialize_state(state, output);
+    
+    return 0;
+}
+
+int chacha20_encrypt(const uint8_t key[32], uint32_t counter, 
+                     const uint8_t nonce[12], const uint8_t* input, 
+                     uint8_t* output, size_t length) {
+    uint8_t keystream[CHACHA20_BLOCK_SIZE];
+    size_t offset = 0;
+    
+    while (length > 0) {
+        /* Generate keystream block */
+        int ret = chacha20_block(key, counter, nonce, keystream);
+        if (ret != 0) {
+            return ret;
+        }
+        
+        /* XOR with input to produce output */
+        size_t block_len = (length < CHACHA20_BLOCK_SIZE) ? length : CHACHA20_BLOCK_SIZE;
+        for (size_t i = 0; i < block_len; i++) {
+            output[offset + i] = input[offset + i] ^ keystream[i];
+        }
+        
+        /* Move to next block */
+        offset += block_len;
+        length -= block_len;
+        counter++;
+        
+        /* Check for counter overflow */
+        if (counter == 0) {
+            return -1; /* Counter wrapped around */
+        }
+    }
+    
+    return 0;
+}

nostr_chacha20.h

@@ -0,0 +1,115 @@
+/*
+ * nostr_chacha20.h - ChaCha20 stream cipher implementation
+ * 
+ * Implementation based on RFC 8439 "ChaCha20 and Poly1305 for IETF Protocols"
+ * 
+ * This is a small, portable implementation for NIP-44 support in the NOSTR library.
+ * The implementation prioritizes correctness and simplicity over performance.
+ */
+
+#ifndef NOSTR_CHACHA20_H
+#define NOSTR_CHACHA20_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * ============================================================================
+ * CONSTANTS AND DEFINITIONS
+ * ============================================================================
+ */
+
+#define CHACHA20_KEY_SIZE    32  /* 256 bits */
+#define CHACHA20_NONCE_SIZE  12  /* 96 bits */
+#define CHACHA20_BLOCK_SIZE  64  /* 512 bits */
+
+/*
+ * ============================================================================
+ * CORE CHACHA20 FUNCTIONS
+ * ============================================================================
+ */
+
+/**
+ * ChaCha20 quarter round operation
+ * 
+ * Operates on four 32-bit words performing the core ChaCha20 quarter round:
+ * a += b; d ^= a; d <<<= 16;
+ * c += d; b ^= c; b <<<= 12;
+ * a += b; d ^= a; d <<<= 8;
+ * c += d; b ^= c; b <<<= 7;
+ * 
+ * @param state[in,out] ChaCha state as 16 32-bit words
+ * @param a, b, c, d    Indices into state array for quarter round
+ */
+void chacha20_quarter_round(uint32_t state[16], int a, int b, int c, int d);
+
+/**
+ * ChaCha20 block function
+ * 
+ * Transforms a 64-byte input block using ChaCha20 algorithm with 20 rounds.
+ * 
+ * @param key[in]       32-byte key
+ * @param counter[in]   32-bit block counter
+ * @param nonce[in]     12-byte nonce
+ * @param output[out]   64-byte output buffer
+ * @return              0 on success, negative on error
+ */
+int chacha20_block(const uint8_t key[32], uint32_t counter, 
+                   const uint8_t nonce[12], uint8_t output[64]);
+
+/**
+ * ChaCha20 encryption/decryption
+ * 
+ * Encrypts or decrypts data using ChaCha20 stream cipher.
+ * Since ChaCha20 is a stream cipher, encryption and decryption are the same operation.
+ * 
+ * @param key[in]           32-byte key
+ * @param counter[in]       Initial 32-bit counter value
+ * @param nonce[in]         12-byte nonce
+ * @param input[in]         Input data to encrypt/decrypt
+ * @param output[out]       Output buffer (can be same as input)
+ * @param length[in]        Length of input data in bytes
+ * @return                  0 on success, negative on error
+ */
+int chacha20_encrypt(const uint8_t key[32], uint32_t counter, 
+                     const uint8_t nonce[12], const uint8_t* input, 
+                     uint8_t* output, size_t length);
+
+/*
+ * ============================================================================
+ * UTILITY FUNCTIONS
+ * ============================================================================
+ */
+
+/**
+ * Initialize ChaCha20 state matrix
+ * 
+ * Sets up the initial 16-word state matrix with constants, key, counter, and nonce.
+ * 
+ * @param state[out]    16-word state array to initialize
+ * @param key[in]       32-byte key
+ * @param counter[in]   32-bit block counter
+ * @param nonce[in]     12-byte nonce
+ */
+void chacha20_init_state(uint32_t state[16], const uint8_t key[32], 
+                         uint32_t counter, const uint8_t nonce[12]);
+
+/**
+ * Serialize ChaCha20 state to bytes
+ * 
+ * Converts 16 32-bit words to 64 bytes in little-endian format.
+ * 
+ * @param state[in]     16-word state array
+ * @param output[out]   64-byte output buffer
+ */
+void chacha20_serialize_state(const uint32_t state[16], uint8_t output[64]);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NOSTR_CHACHA20_H */

otp.code-workspace

@@ -0,0 +1,8 @@
+{
+	"folders": [
+		{
+			"path": "."
+		}
+	],
+	"settings": {}
+}