otter-crypto

otter-crypto wraps otr standard-library cryptography. It has no libcrypto or other C cryptographic dependency. Import leaf modules, not a package root.

Module	Surface
`hash`	MD5, SHA-1, SHA-256, SHA-512
`hmac`	Corresponding keyed hashes
`aes`, `cmac`	AES-128 blocks, CTR32-BE, CBC-MAC, CMAC
`aead`	AES-128-GCM, ChaCha20-Poly1305, XChaCha20-Poly1305
`chacha`, `poly1305`	Stream/MAC primitives
`x25519`	Key exchange
`ed25519`	Keys, deterministic signing, verification
`random`, `wipe`	OS randomness and explicit clearing

import otter_crypto.hash

pub fn main() void {
    digest := hash.Sha256.hash("example")
    _ = digest
}

Ownership and safety

Hash/HMAC contexts are value structs with wipe(). AES key schedules, CBC-MAC, and CMAC own boxed state and require consuming deinit() to clear and free it. Use random.fill for key material. It reports OS randomness errors rather than substituting a deterministic source. Use std.crypto.timing_safe_eql for secret comparisons and std.mem.secure_zero for byte buffers. AEAD decrypt returns an authentication error on invalid input and zeros its destination. In-place decrypt therefore destroys ciphertext on failure. Preserve a separate copy if retry logic needs the ciphertext. MD5 and SHA-1 are available for existing protocol/file-format compatibility. Do not choose them for new security-sensitive designs. Nonce uniqueness and key lifetime remain the caller’s responsibility when using raw AEAD primitives.

Lua

otter_crypto_lua provides otter.crypto with no capability requirement; its operations do not act on external services.

hash(algorithm, data, raw?) and hmac(algorithm, key, data, raw?) return hex by default.
random(n) / random_hex(n) accept 1..4096 bytes.
equal(a, b) compares in constant time.
seal(key32, plain, ad?) uses XChaCha20-Poly1305 with a fresh random nonce.
open(key32, sealed, ad?) authenticates the nonce || ciphertext || tag representation; failure returns nil, "authentication failed".

The host must register the binding; native package imports do not expose Lua functions automatically.

local crypto = require("otter.crypto")
local key = crypto.random(32)
local sealed = crypto.seal(key, "example", "context")
local plain, err = crypto.open(key, sealed, "context")
assert(plain == "example", err)

This example keeps a fresh key only in memory. Applications that retain encrypted data must also define secure key storage and recovery.

Source reference

otr/API.md, otr/api_check.otr, otr/aead.otr, otr/ed25519.otr, otr/lua/crypto.otr in the component repository.

Getting Started

Lua extensions

Libraries

Ownership and safety

Lua

Source reference

​Ownership and safety

​Lua

​Source reference

Ownership and safety

Lua

Source reference