devolutions-crypto

Cryptographic library used in Devolutions products. It is made to be fast, easy to use and misuse-resistant.

Documentation

Usage

• Overview
• Ciphertext Module
  • Symmetric Encryption
  • Asymmetric Encryption
• Key Module
  • Key Generation/Derivation
  • Key Exchange
• PasswordHash Module
• SecretSharing Module
• Signature Module
  • Generating Key Pairs
  • Signing data
  • Signature Verification
• Utils Module
  • Key Generation
  • Key Derivation

Overview

The library is splitted into multiple modules, which are explained below. When dealing with "managed" data, that includes an header and versionning, you deal with structures like Ciphertext, PublicKey, etc.

These all implements TryFrom<&[u8]> and Into<Vec<u8>> which are the implemented way to serialize and deserialize data.

use std::convert::TryFrom as _;
use devolutions_crypto::utils::generate_key;
use devolutions_crypto::ciphertext::{ encrypt, CiphertextVersion, Ciphertext };

let key: Vec<u8> = generate_key(32);

let data = b"somesecretdata";

let encrypted_data: Ciphertext = encrypt(data, &key, CiphertextVersion::Latest).expect("encryption shouldn't fail");

// The ciphertext can be serialized.
let encrypted_data_vec: Vec<u8> = encrypted_data.into();

// This data can be saved somewhere, passed to another language or over the network
// ...
// When you receive the data as a byte array, you can deserialize it into a struct using TryFrom

let ciphertext = Ciphertext::try_from(encrypted_data_vec.as_slice()).expect("deserialization shouldn't fail");

let decrypted_data = ciphertext.decrypt(&key).expect("The decryption shouldn't fail");

assert_eq!(decrypted_data, data);

Ciphertext

This module contains everything related to encryption. You can use it to encrypt and decrypt data using either a shared key of a keypair.
Either way, the encryption will give you a Ciphertext, which has a method to decrypt it.

Symmetric

use devolutions_crypto::utils::generate_key;
use devolutions_crypto::ciphertext::{ encrypt, CiphertextVersion, Ciphertext };

let key: Vec<u8> = generate_key(32);

let data = b"somesecretdata";

let encrypted_data: Ciphertext = encrypt(data, &key, CiphertextVersion::Latest).expect("encryption shouldn't fail");

let decrypted_data = encrypted_data.decrypt(&key).expect("The decryption shouldn't fail");

assert_eq!(decrypted_data, data);

Asymmetric

Here, you will need a PublicKey to encrypt data and the corresponding PrivateKey to decrypt it. You can generate them by using generate_keypair in the Key module.

use devolutions_crypto::key::{generate_keypair, KeyVersion, KeyPair};
use devolutions_crypto::ciphertext::{ encrypt_asymmetric, CiphertextVersion, Ciphertext };

let keypair: KeyPair = generate_keypair(KeyVersion::Latest);

let data = b"somesecretdata";

let encrypted_data: Ciphertext = encrypt_asymmetric(data, &keypair.public_key, CiphertextVersion::Latest).expect("encryption shouldn't fail");

let decrypted_data = encrypted_data.decrypt_asymmetric(&keypair.private_key).expect("The decryption shouldn't fail");

assert_eq!(decrypted_data, data);

Key

For now, this module only deal with keypairs, as the symmetric keys are not wrapped yet.

Generation/Derivation

Using generate_keypair will generate a random keypair.

Asymmetric keys have two uses. They can be used to encrypt and decrypt data and to perform a key exchange.

generate_keypair

use devolutions_crypto::key::{generate_keypair, KeyVersion, KeyPair};

let keypair: KeyPair = generate_keypair(KeyVersion::Latest);

Key Exchange

The goal of using a key exchange is to get a shared secret key between two parties without making it possible for users listening on the conversation to guess that shared key.

1. Alice and Bob generates a KeyPair each.
2. Alice and Bob exchanges their PublicKey.
3. Alice mix her PrivateKey with Bob's PublicKey. This gives her the shared key.
4. Bob mixes his PrivateKey with Alice's PublicKey. This gives him the shared key.
5. Both Bob and Alice has the same shared key, which they can use for symmetric encryption for further communications.

use devolutions_crypto::key::{generate_keypair, mix_key_exchange, KeyVersion, KeyPair};

let bob_keypair: KeyPair = generate_keypair(KeyVersion::Latest);
let alice_keypair: KeyPair = generate_keypair(KeyVersion::Latest);

let bob_shared = mix_key_exchange(&bob_keypair.private_key, &alice_keypair.public_key).expect("key exchange should not fail");

let alice_shared = mix_key_exchange(&alice_keypair.private_key, &bob_keypair.public_key).expect("key exchange should not fail");

// They now have a shared secret!
assert_eq!(bob_shared, alice_shared);

PasswordHash

You can use this module to hash a password and validate it afterward. This is the recommended way to verify a user password on login.

use devolutions_crypto::password_hash::{hash_password, PasswordHashVersion};

let password = b"somesuperstrongpa$$w0rd!";

let hashed_password = hash_password(password, 10000, PasswordHashVersion::Latest);

assert!(hashed_password.verify_password(b"somesuperstrongpa$$w0rd!"));
assert!(!hashed_password.verify_password(b"someweakpa$$w0rd!"));

SecretSharing

This module is used to generate a key that is splitted in multiple Share and that requires a specific amount of them to regenerate the key.
You can think of it as a "Break The Glass" scenario. You can generate a key using this, lock your entire data by encrypting it and then you will need, let's say, 3 out of the 5 administrators to decrypt the data. That data could also be an API key or password of a super admin account.

use devolutions_crypto::secret_sharing::{generate_shared_key, join_shares, SecretSharingVersion, Share};

// You want a key of 32 bytes, splitted between 5 people, and I want a 
// minimum of 3 of these shares to regenerate the key.
let shares: Vec<Share> = generate_shared_key(5, 3, 32, SecretSharingVersion::Latest).expect("generation shouldn't fail with the right parameters");

assert_eq!(shares.len(), 5);
let key = join_shares(&shares[2..5]).expect("joining shouldn't fail with the right shares");

Signature

This module is used to sign data using a keypair to certify its authenticity.

Generating Key Pairs

use devolutions_crypto::signing_key::{generate_signing_keypair, SigningKeyVersion, SigningKeyPair, SigningPublicKey};

let keypair: SigningKeyPair = generate_signing_keypair(SigningKeyVersion::Latest);

Signing Data

use devolutions_crypto::signature::{sign, Signature, SignatureVersion};

let signature: Signature = sign(b"this is some test data", &keypair, SignatureVersion::Latest);

Verifying the signature

use devolutions_crypto::signature::{sign, Signature, SignatureVersion};

assert!(signature.verify(b"this is some test data", &public_key));

Utils

These are a bunch of functions that can be useful when dealing with the library.

Key Generation

This is a method used to generate a random key. In almost all case, the length parameter should be 32.

use devolutions_crypto::utils::generate_key;

let key = generate_key(32);
assert_eq!(32, key.len());

Key Derivation

This is a method used to generate a key from a password or another key. Useful for password-dependant cryptography. Salt should be a random 16 bytes array if possible and iterations should be 10000 or configurable by the user.

use devolutions_crypto::utils::{generate_key, derive_key};
let key = b"this is a secret password";
let salt = generate_key(16);
let iterations = 10000;
let length = 32;

let new_key = derive_key(key, &salt, iterations, length);

assert_eq!(32, new_key.len());

Underlying algorithms

As of the current version:

• Symmetric cryptography uses XChaCha20Poly1305
• Asymmetric cryptography uses Curve25519.
• Asymmetric encryption uses ECIES.
• Key exchange uses x25519, or ECDH over Curve25519
• Password Hashing uses PBKDF2-HMAC-SHA2-256
• Secret Sharing uses Shamir Secret sharing over GF256