https://github.com/jedisct1/zig-charm

A Zig version of the Charm crypto library.
https://github.com/jedisct1/zig-charm

charm crypto cryptography lightweight xoodoo zig zig-package ziglang

Last synced: about 2 months ago
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A Zig version of the Charm crypto library.

• Host: GitHub
• URL: https://github.com/jedisct1/zig-charm
• Owner: jedisct1
• License: mit
• Created: 2020-10-27T17:32:21.000Z (almost 4 years ago)
• Default Branch: main
• Last Pushed: 2024-05-09T19:57:03.000Z (4 months ago)
• Last Synced: 2024-05-10T15:55:10.755Z (4 months ago)
• Topics: charm, crypto, cryptography, lightweight, xoodoo, zig, zig-package, ziglang
• Language: Zig
• Homepage:
• Size: 17.6 KB
• Stars: 73
• Watchers: 5
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-zig - zig-charm🗒️A Zig version of the Charm crypto library

README

        
# charm

A tiny, self-contained cryptography library, implementing authenticated encryption and keyed hashing.

Charm was especially designed for memory-constrained devices, but can also be used to add encryption support to WebAssembly modules with minimal overhead.

Any number of hashing and authenticated encryption operations can be freely chained using a single rolling state.

In this mode, each authentication tag authenticates the whole transcript since the beginning of the session.

The [original implementation](https://github.com/jedisct1/charm) was written in C and is used by the [dsvpn](https://github.com/jedisct1/dsvpn) VPN software.

This is a port to the [Zig](https://ziglang.org) language. It is fully compatible with the C version.

## Usage

### Setting up a session

Charm requires a 256-bit key, and, if the key is reused for different sessions, a unique session identifier (`nonce`):

```zig

var key: [Charm.key_length]u8 = undefined;

std.crypto.random.bytes(&key);

var charm = Charm.new(key, null);

```

### Hashing

```zig

const h = charm.hash("data");

```

### Authenticated encryption

#### Encryption

```zig

const tag = charm.encrypt(msg[0..]);

```

Encrypts `msg` in-place and returns a 128-bit authentication tag.

#### Decryption

Starting from the same state as the one used for encryption:

```zig

try charm.decrypt(msg[0..], tag);

```

Returns `error.AuthenticationFailed` if the authentication tag is invalid for the given message and the previous transcript.

## Security guarantees

128-bit security, no practical limits on the size and length of messages.

## Other implementations:

- [charm](https://github.com/jedisct1/charm) original implementation in C.

- [charm.js](https://github.com/jedisct1/charm.js) a JavaScript (TypeScript) implementation.