class ROTP::OTP

def generate_otp(input, padded=true)

Options Hash: (**padded)
  • (false) (Boolean) -- Output the otp as a 0 padded string

Parameters:
  • input (Integer) -- the number used seed the HMAC 
def generate_otp(input, padded=true)
  hmac = OpenSSL::HMAC.digest(
    OpenSSL::Digest.new(digest),
    byte_secret,
    int_to_bytestring(input)
  )
  offset = hmac[-1].ord & 0xf
  code = (hmac[offset].ord & 0x7f) << 24 |
    (hmac[offset + 1].ord & 0xff) << 16 |
    (hmac[offset + 2].ord & 0xff) << 8 |
    (hmac[offset + 3].ord & 0xff)
  if padded
    (code % 10 ** digits).to_s.rjust(digits, '0')
  else
    code % 10 ** digits
  end
end