OTP

This is a Golang OTP library compatible with google-authenticator APP.

Installation

$ go get github.com/huk10/go-otp

Usage

Check API docs at https://godoc.org/github.com/huk10/go-otp

Time-based OTPs

secret := otp.Base32Encode(otp.RandomSecret(20))
totp := otp.NewTOTP(secret)

// Get the token of the current time
_ = totp.Now()

// Get the token for the specified time
token := totp.At(time.Unix(1704075000000, 0))

// otp verify
totp.Verify(token,  time.Unix(1704075000000, 0))

// get qrcode 
png, err := totp.KeyURI("alice@google.com", "Example").QRCode()
if err != nil {
    panic(err)
}
// qrcode write to a file
err = os.WriteFile("./qrcode.png", png, 0666)

// get uri
_ = totp.KeyURI("alice@google.com", "Example").URI().String()

Counter-based OTPs

secret := otp.Base32Encode(otp.RandomSecret(20))
hotp := otp.NewHOTP(secret)

// Get the token corresponding to counter 1
token := hotp.At(1)

// otp verify
hotp.Verify(token, 1)

// get qrcode 
png, err := hotp.KeyURI("alice@google.com", "Example").QRCode()
if err != nil {
    panic(err)
}
// qrcode write to a file
err = os.WriteFile("./qrcode.png", png, 0666)

// get uri
_ = hotp.KeyURI("alice@google.com", "Example").URI().String()

Generate random secret

// generate a 20 byte random secret
secret := otp.RandomSecret(20)
// base32 encode
str := otp.Base32Encode(secret)

Google Authenticator Compatible

This library works with the Google Authenticator APP.

// secret 
secret := otp.Base32Encode(otp.RandomSecret(20))

// totp
otp.NewTOTP(secret).KeyURI("alice@google.com", "Example").URI().String()

// hotp
otp.NewHOTP(secret, otp.WithCounter(10)).KeyURI("alice@google.com", "Example").URI().String()

You can use the URI generated by the above code as the QR code content and use the Google Authenticator APP to scan the code and import it.

Working example

Use Google Authenticator to scan the QR code below.

Now run the following and compare the output:

package main

import (
	"fmt"
	"github.com/huk10/go-otp"
)

func main() {
	totp := otp.NewTOTP("J3W2XPZP5HDYXYRB4HS6ZLU6M6VBO6C6")
	token := totp.Now()
	fmt.Println("Current OTP is", token)
}

Links

• HOTP: An HMAC-Based One-Time Password Algorithm
• TOTP: Time-Based One-Time Password Algorithm

License

go-otp is licensed under the MIT License