anar-otp - Unified HOTP & TOTP Package in Go

anar-otp is a comprehensive Go package for generating and verifying HOTP (HMAC-based One-Time Passwords) and TOTP (Time-based One-Time Passwords). It also supports QR code generation for provisioning URIs.

Features

• Supports HOTP and TOTP.
• Configurable digits, hashing algorithms (SHA1, SHA256, SHA512), periods, and skew.
• Automatic secret generation per algorithm.
• QR code generation (PNG and Base64) for easy provisioning.
• Convenient unified OTP struct for easy handling.
• Verification with optional window or skew.

Installation

go get codeberg.org/anarproject/anar-otp

Usage

Generate a secret

package main

import (
    "fmt"
    "codeberg.org/anarproject/anar-otp"
)

func main() {
    secret, err := anar_otp.GenerateSecretForAlgorithm(anar_otp.SHA1)
    if err != nil {
        panic(err)
    }
    fmt.Println("Generated Secret:", secret)
}

HOTP Example

secret := []byte("mysecretkey")
hotp := anar_otp.NewHOTP(secret, 6, anar_otp.SHA1)

code, _ := hotp.Generate(uint64(1))
fmt.Println("HOTP code:", code)

valid, _ := hotp.Verify(code, uint64(1))
fmt.Println("HOTP valid?", valid)

TOTP Example

secretBase32 := "JBSWY3DPEHPK3PXP"
totp, _ := anar_otp.NewTOTP(secretBase32, nil)

code, _ := totp.Generate(time.Now())
fmt.Println("TOTP code:", code)

valid, _ := totp.Verify(code, time.Now())
fmt.Println("TOTP valid?", valid)

Generate QR Code

pngData, _ := totp.QRCodePNG("MyApp", "user@example.com", 256)
// Save pngData to file

base64Str, _ := totp.QRCodeBase64("MyApp", "user@example.com", 256)
fmt.Println("QR Code Base64:", base64Str)

Provisioning URI

uri, _ := totp.ProvisioningURI("MyApp", "user@example.com")
fmt.Println("Provisioning URI:", uri)

Configuration Options

• Digits: Number of digits (default 6)
• Algorithm: SHA1, SHA256, SHA512
• Period: Time period for TOTP (default 30s)
• Skew: Allowed clock skew for TOTP verification

Recommended secret lengths per algorithm:

| Algorithm | Secret Length (bytes) | | | | | SHA1 | 20 | | SHA256 | 32 | | SHA512 | 64 |

License

This library is licensed under the GNU Lesser General Public License (LGPL) v3.0.

Author

Ali Miracle