CODEWITHSUNDEEP
node.jsnpmhashmd5
ThisRestlessPilgrim
ThisRestlessPilgrim

Reputation: 541

Different results from MD5 libraries

I need to hash some data using MD5. I wanted to test the performance of difference libraries. However, I'm noticing that I'm getting different hashes of the same data, depending upon which library is being used:

Generating data...

Hashing data with 'md5' library...
         Hash: 1b37c84ebc8426e19d3b1797b6e320c6
         Duration: 0.848s

Hashing data with 'object-hash' library...
         Hash: f046296e8016b5632e6a1d1ebc885892
         Duration: 0.032s

Hashing data with 'create-hash' library...
         Hash: 1b37c84ebc8426e19d3b1797b6e320c6
         Duration: 0.023s

I would have expected the same hash to be shown for both libraries. Any ideas? My code is below...

const generateData = () => {
    console.log('Generating data...')
    let data = "";
    for (let i = 0; i < 1000000; i++) {
        data += "1234567890";
    }
    console.log()    
    return data;
}

const convertToUInt8Array = (s) => {
    var result = [];
    for(var i = 0; i < s.length; i+=2)
    {
        result.push(parseInt(s.substring(i, i + 2), 16));
    }
    result = Uint8Array.from(result)
    return result;
}

const hashData = (name, hashingFunction, data) => {
    console.log(`Hashing data with '${name}' library...`)
    const start = new Date()
    const hash = hashingFunction(data)
    const end = new Date()
    console.log(`\t Hash: ${hash}`)
    const duration = (end - start) / 1000
    console.log(`\t Duration: ${duration}s`)
    console.log()
}

const hashWithMD5 = (data) => {
    const md5 = require('md5')
    return md5(data)
}

const hashWithObjectHash = (data) => {
    const objectHash = require('object-hash')
    return objectHash.MD5(data)
} 

const hashWithCreateHash = (data) => {
    const createHash = require('create-hash')
    const hash = createHash('md5')
    hash.update(data)
    return hash.digest('hex')
}

const data = generateData()
hashData('md5', hashWithMD5, data)
hashData('object-hash', hashWithObjectHash, data)
hashData('create-hash', hashWithCreateHash, data)

Upvotes: 4

Views: 484

Answers (1)

Patrick Roberts
Patrick Roberts

Reputation: 51977

object-hash hashes the object, not the string value. The implementation prepends 

'string:' + string.length + ':'

to the input string and does an MD5 hash of that. You can confirm this by modifying hashWithCreateHash to generate a hash of the same input:

const hashWithCreateHash = (data) => {
    const createHash = require('create-hash')
    const hash = createHash('md5')
    hash.update(`string:${data.length}:${data}`) // instead of hash.update(data)
    return hash.digest('hex')
}

Hashing data with 'create-hash' library...
         Hash: f046296e8016b5632e6a1d1ebc885892
         Duration: 0.023s

Upvotes: 2

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