[Java] Private Key Signing - Public Key Verifying

Private key 서명과 이를 public key로 인증하는 Java 예제

1. data 생성
2. private key signing
3. public key verify

KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(2048);

KeyPair keyPair = keyGen.generateKeyPair();
PublicKey publicKey = keyPair.getPublic();
PrivateKey privateKey = keyPair.getPrivate();

// create a data
byte[] data = new byte[10000];
ThreadLocalRandom.current().nextBytes(data);

// sign using the private key
Signature sig = Signature.getInstance("SHA256withRSA");
sig.initSign(privateKey);
sig.update(data);
byte[] signature = sig.sign();

// verify signature using the public key
sig.initVerify(publicKey);
sig.update(data);

boolean keyPairMatches = sig.verify(signature);