go SHA256WithRSA

In Go,SHA256WithRSArefers to RSA digital signatures with SHA-256 hashing, a common standard for signing and verification. Here's how to implement it:

1. Generate RSA Key Pair

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package main import ( "crypto/rand" "crypto/rsa" "crypto/x509" "encoding/pem" "fmt" "os" ) func generateKeys() (*rsa.PrivateKey, error) { // Generate 2048-bit RSA key pair privateKey, err := rsa.GenerateKey(rand.Reader, 2048) if err != nil { return nil, err } return privateKey, nil } // Save keys to PEM files func savePrivateKey(key *rsa.PrivateKey, filename string) error { file, err := os.Create(filename) if err != nil { return err } defer file.Close() privateKeyBytes := x509.MarshalPKCS1PrivateKey(key) privateKeyPEM := &pem.Block{ Type: "RSA PRIVATE KEY", Bytes: privateKeyBytes, } return pem.Encode(file, privateKeyPEM) }

2. Sign Data with SHA256 + RSA

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import ( "crypto" "crypto/rand" "crypto/rsa" "crypto/sha256" ) func signData(privateKey *rsa.PrivateKey, data []byte) ([]byte, error) { // Hash the data with SHA-256 hash := sha256.Sum256(data) // Sign the hash using RSA-PSS (recommended) or PKCS#1 v1.5 signature, err := rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA256, hash[:]) if err != nil { return nil, err } return signature, nil }

3. Verify Signature

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func verifySignature(publicKey *rsa.PublicKey, data, signature []byte) error { hash := sha256.Sum256(data) // Verify the signature err := rsa.VerifyPKCS1v15(publicKey, crypto.SHA256, hash[:], signature) if err != nil { return fmt.Errorf("signature verification failed: %w", err) } return nil }

4. Complete Example

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package main import ( "crypto" "crypto/rand" "crypto/rsa" "crypto/sha256" "fmt" ) func main() { // Generate keys privateKey, err := rsa.GenerateKey(rand.Reader, 2048) if err != nil { panic(err) } // Data to sign data := []byte("Hello, SHA256WithRSA!") // Sign signature, err := signData(privateKey, data) if err != nil { panic(err) } fmt.Printf("Signature: %x\n", signature) // Verify publicKey := &privateKey.PublicKey err = verifySignature(publicKey, data, signature) if err != nil { panic(err) } fmt.Println("✅ Signature verified successfully!") }

Key Points

• crypto.SHA256: Specifies SHA-256 as the hash algorithm

• rsa.SignPKCS1v15: PKCS#1 v1.5 padding (widely compatible)

• rsa.SignPSS: More secure PSS padding (recommended for new systems)

• Hash first: Always hash data before signing; RSA operates on the hash digest

Thecrypto/x509andencoding/pempackages handle key serialization for storage and exchange.