@libp2p/crypto/dist/src/keys/key-stretcher.js

Crypto primitives for libp2p

import { InvalidParametersError } from '@libp2p/interface';
import { concat as uint8ArrayConcat } from 'uint8arrays/concat';
import { fromString as uint8ArrayFromString } from 'uint8arrays/from-string';
import * as hmac from '../hmac/index.js';
const cipherMap = {
    'AES-128': {
        ivSize: 16,
        keySize: 16
    },
    'AES-256': {
        ivSize: 16,
        keySize: 32
    },
    Blowfish: {
        ivSize: 8,
        keySize: 32
    }
};
/**
 * Generates a set of keys for each party by stretching the shared key.
 * (myIV, theirIV, myCipherKey, theirCipherKey, myMACKey, theirMACKey)
 */
export async function keyStretcher(cipherType, hash, secret) {
    if (cipherType !== 'AES-128' && cipherType !== 'AES-256' && cipherType !== 'Blowfish') {
        throw new InvalidParametersError('Cipher type was missing or unsupported');
    }
    if (hash !== 'SHA1' && hash !== 'SHA256' && hash !== 'SHA512') {
        throw new InvalidParametersError('Hash type was missing or unsupported');
    }
    if (secret == null || !(secret instanceof Uint8Array)) {
        throw new InvalidParametersError('Secret was missing or an incorrect type');
    }
    const cipher = cipherMap[cipherType];
    const cipherKeySize = cipher.keySize;
    const ivSize = cipher.ivSize;
    const hmacKeySize = 20;
    const seed = uint8ArrayFromString('key expansion');
    const resultLength = 2 * (ivSize + cipherKeySize + hmacKeySize);
    const m = await hmac.create(hash, secret);
    let a = await m.digest(seed);
    const result = [];
    let j = 0;
    while (j < resultLength) {
        const b = await m.digest(uint8ArrayConcat([a, seed]));
        let todo = b.length;
        if (j + todo > resultLength) {
            todo = resultLength - j;
        }
        result.push(b);
        j += todo;
        a = await m.digest(a);
    }
    const half = resultLength / 2;
    const resultBuffer = uint8ArrayConcat(result);
    const r1 = resultBuffer.subarray(0, half);
    const r2 = resultBuffer.subarray(half, resultLength);
    const createKey = (res) => ({
        iv: res.subarray(0, ivSize),
        cipherKey: res.subarray(ivSize, ivSize + cipherKeySize),
        macKey: res.subarray(ivSize + cipherKeySize)
    });
    return {
        k1: createKey(r1),
        k2: createKey(r2)
    };
}
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