Multikey

A Rust implementation of the multiformats multikey specification and nonce specification.

Current Status

This implementation of the Multikey specification supports both public key and secret key cryptography keys. For public key cryptography, it supports Ed25519, Nist P256, P384, and P521, as well as BLS12-381 G1/G2 curves. For secret key cryptography it supports ChaCha-256 keys.

This implementation supports encrypting/decrypting keys using ChaCha20-Poly1305 AEAD with keys derived with Bcrypt KDF from a preimage.

When using BLS12-381 keys, this implementations supports threshold key splitting and combining as well as threshold signing and verifying.

This crate also supports converting to/from SSH format keys using the ssh-key crate. This gives full OpenSSH compatibility for reading in OpenSSH serialized keys and converting them to Multikey format. This even includes non-standard SSH key protocols such as secp256k1 and BLS12-381 G1/G2 keys through the use of RFC 4251 standard for "additional algorithms" names using the "@multikey" domain suffix. For instance, using this crate, an secp256k1 Multikey converted to an SSH format key has the algorithm name "secp256k1@multikey". A BLS12-381 G1 key share converted to SSH format has the algorithm name "bls12_381-g1-share@multkey".

For the technical details of the design of Multikey or Nonce, please refer to the specifications linked above.

Introduction

This is a Rust implementation of a multicodec format for encryption keys. The design of the format is intentionally abstract to support any kind of encryption key in any state (e.g. encrypted or unencrypted). This format should be best thought of as a container of key material with abstract, algorithm- specific views and a generic and self-describing data storage format.

Every piece of data in the serialized Multikey object either has a known-fixed size or a self-describing variable size such that software processing these objects do not need to support all encryption algorithms to be able to accurately calculate the size of the serialized object and skip over it if needed.

Views on the Multikey Data

To provide an abstract interface to encryption keys for all algorithms, this Multikey crate provides "views" on the Multikey data. These are read-only abstract interfaces to the Multikey attributes with implementations for different supporting encryption algorithms.

Currently the set of views provide generic access to the general attributes (multikey::AttrView) of the Multikey, the key data (multikey::DataView), as well as views on the KDF attributes (multikey::KdfAttrView), and cipher attributes (multikey::CipherAttrView) for encrypted Multikeys. For algorithms that support threshold operations there is a threshold attributes view (multikey::ThresholdAttrView).

For operations you can do with a Multikey, there is a cipher view (multikey::CipherView) for encrypting/decrypting a Multikey, a conversion view (multikey::ConvView) for converting the Multikey to other formats (e.g. to/from ssh key format and secret keys to public keys), a fingerprint view (multikey::FingerprintView) for getting a key fingerprint using a given hashing codec, a KDF view (multikey::KdfView) for generating cipher keys for use by a cipher view to encrypt/decrypt the Multikey, a threshold view (multikey::ThresholdView) for key splitting and combining keys, and lastly a sign view (multikey::SignView) and verify view (multikey::VerifyView) for creating and verifying Multisig digital signatures.

It is important to note that the operations that seem to mutate the Multikey (e.g. encrypt, decrypt, convert, etc) in fact do a copy-on-write (CoW) operation and return a new Multikey with the mutation applied.