Using Hmac and base64 to sign

Question

I am trying to connect to a server, and the password is a bit tricky. the password should be generated like this

base64(hmac(secret,timestamp:userid)

I have the secret and userid we can consider them SECRET and 0. I am using Flutter and in Flutter hmac function takes a HASH and a list so I cant hash two strings/

can you help with this issue?

Answer 1

The crypto package contains an implementation of HMAC. As you would expect, it needs a key and a message. See the sample code:

var key = utf8.encode('p@ssw0rd'); // key gets converted to bytes (using utf8)
var bytes = utf8.encode("foobar"); // message gets converted to bytes (utf8)

var hmacSha256 = Hmac(sha256, key); // HMAC-SHA256 (using the key bytes)
var digest = hmacSha256.convert(bytes); // the hmac is generated from the message

In your case you'd use:

var key = utf8.encode('SECRET'); 
var bytes = utf8.encode('0');

var hmacSha256 = Hmac(sha256, key); // HMAC-SHA256
var digest = hmacSha256.convert(bytes);
print(base64.encode(digest.bytes));

All HMACs need a hash function. You need to find out which HMAC hash your API requires.