function GoogleAuthenticatorCode(string secret)
key := base32decode(secret)
message := floor(current Unix time / 30)
hash := HMAC-SHA1(key, message)
offset := last nibble of hash
truncatedHash := hash[offset..offset+3] //4 bytes starting at the offset
Set the first bit of truncatedHash to zero //remove the most significant bit
code := truncatedHash mod 1000000
pad code with 0 until length of code is 6
return code
function GoogleAuthenticatorCode(string secret)
key := base32decode(secret)
message := counter encoded on 8 bytes
hash := HMAC-SHA1(key, message)
offset := last nibble of hash
truncatedHash := hash[offset..offset+3] //4 bytes starting at the offset
Set the first bit of truncatedHash to zero //remove the most significant bit
code := truncatedHash mod 1000000
pad code with 0 until length of code is 6
return code