How to create a hash using Web Crypto API?

Question

I'm trying to create SHA-1 hash on the client-side. I'm trying to do this with Web Crypto API but when I'm comparing the output to what various online tools give me, the result is completely different. I think the problem is in ArrayBuffer to Hex conversion. Here is my code:

function generateHash() {
            var value = "mypassword";
            var crypto = window.crypto;
            var buffer = new ArrayBuffer(value);
            var hash_bytes = crypto.subtle.digest("SHA-1", buffer);
            hash_bytes.then(value => document.write([...new Uint8Array(value)].map(x => x.toString(16).padStart(2, '0')).join('')));
        }

Output of document.write should be:

91dfd9ddb4198affc5c194cd8ce6d338fde470e2

But it's not, I get a completely different hash of different length (should be 40). Could I have some advise on the problem? Thanks.

Answer 1

The problem seems to be more the input conversion from a string to an ArrayBuffer . Eg with str2ab() the code works:

 generateHash(); function generateHash() { var value = "mypassword"; var crypto = window.crypto; var buffer = str2ab(value); // Fix var hash_bytes = crypto.subtle.digest("SHA-1", buffer); hash_bytes.then(value => document.write([...new Uint8Array(value)].map(x => x.toString(16).padStart(2, '0')).join(''))); } // https://stackoverflow.com/a/11058858 function str2ab(str) { const buf = new ArrayBuffer(str.length); const bufView = new Uint8Array(buf); for (let i = 0, strLen = str.length; i < strLen; i++) { bufView[i] = str.charCodeAt(i); } return buf; }

with the expected output:

91dfd9ddb4198affc5c194cd8ce6d338fde470e2