Crystal bindings for Monocypher
3.1.1 Latest release released

Crystal wrapper for a cryptographic library Monocypher (Official site, Github page)

Note: Sources of Monocypher (version 2.0.5 currently) are included in the shard and will be linked statically with application. On the other hand, if is present in library paths at the time of compilation, linker seems to prefer dynamic linking.


  1. Add this to your application's shard.yml:
    github: konovod/monocypher
  1. shards update will install a shard and compile Monocypher static library. So you need clang or gcc.


  1. The wrapper is created with an additional requirement - using a crypto library for encrypting/decrypting of messages shouldn't cause heap allocations. So it doesn't provide function plaintext = Crypto.unlock(ciphertext, key) (as it will require allocation of plaintext every time message being decrypted). Instead it provide Crypto.decrypt(key: Bytes, input: Bytes, output: Bytes) function that will operate on preallocated buffers.
  2. Most functions receive named arguments. This makes code slightly more verbose, but hopefully will prevent messing up arguments order.

Example of usage:

require "monocypher"

channel = Channel(Bytes).new # should be fixed size in real apps

alice_secret =
alice_public = alice_secret)
bob_secret =
bob_public = bob_secret)

# sender part
spawn do
  alice_shared = alice_secret, their_public: bob_public)
  message = "This is a test message русский текст"
  plaintext = message.to_slice
  ciphertext = + Crypto::OVERHEAD_SYMMETRIC)
  Crypto.encrypt(key: alice_shared, input: plaintext, output: ciphertext)
  channel.send ciphertext

# receiver part
bob_shared = bob_secret, their_public: alice_public)
ciphertext = channel.receive
result = - Crypto::OVERHEAD_SYMMETRIC)
Crypto.decrypt(key: bob_shared, input: ciphertext, output: result)

check spec dir for more usage examples (TODO - other examples)


Monocypher includes functions for cryptographic hashes Blake2b and SHA-512, they are wrapped with simple crystal functions (TODO - API for incremental hashing. How it should looks?)

# "cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e"

Crypto.blake2b("abc".to_slice, key: "".to_slice, hash_size: 64).hexstring
# same as Crypto.blake2b("abc".to_slice).hexstring
# ba80a53f981c4d0d6a2797b69f12f6e94c212f14685ac4b74b12bb6fdbffa2d17d87c5392aab792dc252d5de4533cc9518d38aa8dbf1925ab92386edd4009923
  github: axentro/
  version: ~> 3.1.1
License MIT
Crystal 0.35.1


Dependencies 0

Development Dependencies 0

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