How to integrate OTP-Java with Spring Boot for 2FA?

Add OTP-Java as a dependency and create service beans for OTP generation and verification. You'll need to implement custom authentication providers in Spring Security, as the library doesn't offer direct integrations out of the box.

OTP-Java vs Google Authenticator library: which is better for Java?

OTP-Java is a pure Java, dependency-free library focused on RFC standards, ideal for lightweight projects. Google's library might have more features but could tie you to their ecosystem; choose OTP-Java for vendor-neutral compliance.

How to generate a secure secret in OTP-Java?

Use the SecretGenerator.generate() method for a default 160-bit Base32-encoded secret, or specify a custom bit length like SecretGenerator.generate(512) for stronger security, as detailed in the HOTP initialization section.

Does OTP-Java support SHA-256 and SHA-512 for TOTP?

Yes, it supports HMAC algorithms SHA1, SHA256, and SHA512 for both HOTP and TOTP. Configure it via the builder's withAlgorithm() method, as shown in the usage examples for custom setups.

How to handle clock drift in TOTP verification with OTP-Java?

Use the verify() method with a delay window parameter, such as hotp.verify(code, counter, 2) or totpGenerator.verify(code, delayWindow), to account for time synchronization issues, mentioned in the OTP verification feature.

Can OTP-Java be used in Android applications?

Yes, it's a Java library with no Android-specific dependencies, so it can be integrated into Android apps. However, ensure secure secret storage using Android Keystore and handle permissions appropriately.

Open-Awesome

OTP-Java

MITJavav2.2.0

A lightweight Java library for generating and verifying HOTP and TOTP one-time passwords compliant with RFC 4226 and RFC 6238.

GitHub

245 stars41 forks0 contributors

What is OTP-Java?

OTP-Java is a Java library for generating and verifying one-time passwords used in two-factor authentication systems. It implements both HMAC-based one-time passwords (HOTP) as defined in RFC 4226 and time-based one-time passwords (TOTP) as per RFC 6238. The library simplifies adding OTP functionality to Java applications with a clean, builder-based API.

Target Audience

Java developers building applications that require two-factor authentication, such as web services, APIs, or enterprise systems needing secure user login flows.

Value Proposition

Developers choose OTP-Java for its minimal footprint, strict compliance with RFC standards, and ease of integration—offering a pure Java solution without external dependencies. Its support for OTPAuth URIs and flexible configuration makes it ideal for projects requiring reliable, standards-based OTP generation.

Overview

A small and easy-to-use one-time password generator library for Java implementing RFC 4226 (HOTP) and RFC 6238 (TOTP).

Use Cases

Best For

Adding two-factor authentication to Java web applications
Implementing TOTP-based login systems for APIs
Generating OTPAuth URIs for authenticator app onboarding
Verifying one-time passwords with configurable delay windows
Creating secure backup code systems alongside OTP
Building authentication libraries or SDKs in Java

Not Ideal For

Applications requiring built-in recovery code generation for 2FA fallback
Projects in non-Java ecosystems needing cross-platform or native libraries
Teams wanting an all-in-one authentication solution with user management and OTP delivery

Pros & Cons

Pros

Standards Compliance

Implements both HOTP (RFC 4226) and TOTP (RFC 6238), ensuring compatibility with industry-standard authenticator apps and adherence to specifications.

Dependency-Free Design

Has no external dependencies, making it lightweight and easy to integrate without adding bloat, as emphasized in the philosophy section.

Flexible API Configuration

Uses builder patterns to customize password length, HMAC algorithms (SHA1, SHA256, SHA512), and time periods, with clear examples in the usage section.

OTPAuth URI Integration

Supports creating and parsing OTPAuth URIs for seamless onboarding with authenticator apps, as demonstrated in the generation and initialization examples.

Cons

Missing Recovery Code Support

The README explicitly states recovery code generation is not included, requiring separate implementation for complete 2FA systems, which adds development overhead.

Limited Framework Integrations

Being a standalone library, it lacks built-in integrations with popular frameworks like Spring Security, necessitating custom setup for seamless use in enterprise applications.

Basic Error Handling

Methods throw generic IllegalStateException without detailed error context, as seen in code snippets, which can complicate debugging and error management.

Frequently Asked Questions

Related Projects

Tink

Tink is a multi-language, cross-platform, open source library that provides cryptographic APIs that are secure, easy to use correctly, and hard(er) to misuse.

Stars13,543

Forks1,193

Last commit2 years ago

jjwt

Java JWT: JSON Web Token for Java and Android

Stars11,138

Forks1,398

Last commit19 days ago

Keywhiz

A system for distributing and managing secrets

Stars2,624

Forks213

Last commit3 years ago

pac4j

Security engine for Java (authentication, authorization, multi frameworks): OpenID Connect, SAML2, CAS, OAuth, LDAP, JWT...

Stars2,537

Forks712

Last commit1 day ago

Community-curated · Updated weekly · 100% open source

Found a gem we're missing?

Open-Awesome is built by the community, for the community. Submit a project, suggest an awesome list, or help improve the catalog on GitHub.

Submit a project Star on GitHub