CryptoJS将单词数组一分为二

Question

I'm not too handy with byte conversions, so I want to make sure I'm not doing anything dangerous.

I'm simply generating a 512 bit key using CryptoJS pbkdf2.

I then want to split this key in half to generate two 256 bit keys.

generateKeyPair = function(input, salt) {
     var output = CryptoJS.PBKDF2(input, salt, { keySize: 512/32 });

     var firstHalf = _.clone(output);
     var secondHalf = _.clone(output);
     var sigBytes = output.sigBytes/2;

     firstHalf.words = output.words.slice(0, 10);
     secondHalf.words = output.words.slice(10, 20);
     firstHalf.sigBytes = sigBytes;
     secondHalf.sigBytes = sigBytes;

     return [firstHalf.toString(), secondHalf.toString()];
   }

The output I get for generateKeyPair("hello", "world") is:

["798ef2617367d80daeacf8b457af7903eebf6d1f384c9fed762b14186036e912", "0a9782aa773bdafcd9cd259e95381ac9ab26d026fe6a3375a93dc6b2a69e7ac3"]

The underscore here is using lodash. Does this look right?

Answer 1

Your solution seems fine. I recently solved this problem just by splitting the hex string in half. My example takes a key in WordArray format and returns each half in WordArray format.

function splitKey(key) {
    const keyString = key.toString()
    const firstHalf = keyString.slice(0,keyString.length/2)
    const secondHalf = keyString.slice(keyString.length/2,keyString.length)

    return [CryptoJS.enc.Hex.parse(firstHalf), CryptoJS.enc.Hex.parse(secondHalf)]
}