This package provides a convenient way of generarting Time-based One-Time Passwords in accordance with IETF's RFC6238.

Hash-based One-Time Password Algorithm(HOTP)uses a counter as a moving factor while generating the OTP. This counter is hashed using an HMAC hashing algorithms (HAMC-SHA1, HMAC-SHA256 or HMAC-512). TOTP builds on on HOTP by deriving the moving factor from UNIX time instead of a counter.

TOTP can be used to create OTPs containing more than 6 digits. Users can choose between the HMAC-SHA1, HMAC-SHA256 and HMAC-SHA512 for generating TOTPs.

package main

import (
 "github.com/kelsier27/totp"
 "fmt"
)

func main() {
  var sharedSecret = "3132333435363738393031323334353637383930"
  otpgen := totp.NewDefaultTOTP(sharedSecret)
  totp := otpgen.GenerateTOTP("1970-01-01T00:00:59Z")
  fmt.Println(totp) // output - 94287082
}

TOTP can be installed using go get

go get github.com/kelsier27/totp

1. Obtain TOTPConfig object

Before generating the OTP, we need to obtain a TOTPConfig object. The default objects generate a 8-digit TOTP using T0 as Epoch time 1970-01-01T00:00:00Z and Time Step X as 30s. To get the default TOTPConfig, use one of the following functions depending on the choice of HMAC algorithm

• NewDefaultSHA1
• NewDefaultSHA256
• NewDefaultSHA512

2. Generate TOTP

Once we obtain a config object, we can call the GenerateTOTP method. This method takes a time string as the input and returns a TOTP string.