Go RSA Library

A simple and secure Go library for RSA encryption, decryption, signing, and verification. This library supports OAEP, PSS, and PKCS#1 v1.5 schemes and enforces NIST standards for key sizes.

Features

• Key Generation: Generates RSA key pairs with a minimum size of 2048 bits (NIST standard).
• Encryption/Decryption:
  • RSA-OAEP (with SHA-256) - Recommended
  • RSA-PKCS#1 v1.5 - Deprecated (NIST recommends OAEP)
• Signing/Verification:
  • RSA-PSS (with SHA-256) - Recommended
  • RSA-PKCS#1 v1.5 (with SHA-256)
• Key Management: Import and export keys in PEM format.

NIST Compliance

This library enforces NIST recommendations:

• Minimum Key Size: 2048 bits. Key generation will fail for smaller sizes.
• Hash Function: SHA-256 is used for OAEP and PSS.
• Encryption: RSA-OAEP is the recommended scheme. PKCS#1 v1.5 is marked as deprecated.

Installation

go get github.com/fawwazid/go-rsa

Usage

Import the package

import (
	"fmt"
	"log"

	gorsa "github.com/fawwazid/go-rsa"
)

1. Generate Keys

// Generate a new RSA key pair (minimum 2048 bits)
priv, pub, err := gorsa.GenerateKeys(2048)
if err != nil {
    log.Fatalf("Failed to generate keys: %v", err)
}

2. Encryption and Decryption (OAEP)

Recommended for new applications.

msg := []byte("Secret Message")
label := []byte("optional-label")

// Encrypt
ciphertext, err := gorsa.EncryptOAEP(pub, msg, label)
if err != nil {
    log.Fatal(err)
}

// Decrypt
plaintext, err := gorsa.DecryptOAEP(priv, ciphertext, label)
if err != nil {
    log.Fatal(err)
}
fmt.Printf("Decrypted: %s\n", plaintext)

3. Encryption and Decryption (PKCS#1 v1.5) [Deprecated]

Supported for legacy compatibility only. NIST recommends using OAEP.

msg := []byte("Secret Message")

// Encrypt
ciphertext, err := gorsa.EncryptPKCS1v15(pub, msg)
if err != nil {
    log.Fatal(err)
}

// Decrypt
plaintext, err := gorsa.DecryptPKCS1v15(priv, ciphertext)
if err != nil {
    log.Fatal(err)
}

4. Signing and Verification (PSS)

Recommended for new applications.

// Sign
signature, err := gorsa.SignPSS(priv, msg)
if err != nil {
    log.Fatal(err)
}

// Verify
err = gorsa.VerifyPSS(pub, msg, signature)
if err != nil {
    log.Fatal("Verification failed")
}
fmt.Println("Signature verified!")

5. Signing and Verification (PKCS#1 v1.5)

Supported for legacy compatibility.

msg := []byte("Secret Message")

// Sign
signature, err := gorsa.SignPKCS1v15(priv, msg)
if err != nil {
    log.Fatal(err)
}

// Verify
err = gorsa.VerifyPKCS1v15(pub, msg, signature)
if err != nil {
    log.Fatal("Verification failed")
}

6. Export and Import Keys (PEM)

// Export to PEM
privPEM, err := gorsa.PrivateKeyToPEM(priv)
if err != nil {
    log.Fatal(err)
}
pubPEM, err := gorsa.PublicKeyToPEM(pub)
if err != nil {
    log.Fatal(err)
}

fmt.Printf("Private Key:\n%s\n", privPEM)
fmt.Printf("Public Key:\n%s\n", pubPEM)

// Import from PEM
parsedPriv, err := gorsa.ParsePrivateKeyFromPEM(privPEM)
if err != nil {
    log.Fatal(err)
}

parsedPub, err := gorsa.ParsePublicKeyFromPEM(pubPEM)
if err != nil {
    log.Fatal(err)
}

License

This project is licensed under the MIT License - see the LICENSE file for details.