如何用私鑰對字符串進行簽名

Question

如果我已經將私鑰作為byte[]或String如何使用SHA1withRSA獲取字符串的簽名？

Answer 1

我猜你說的是你事先知道密鑰對，並想用它簽名/驗證。

請看下面的代碼。

import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.Signature;

import sun.misc.BASE64Encoder;

public class MainClass {
    public static void main(String[] args) throws Exception {

        KeyPair keyPair = getKeyPair();

        byte[] data = "test".getBytes("UTF8");

        Signature sig = Signature.getInstance("SHA1WithRSA");
        sig.initSign(keyPair.getPrivate());
        sig.update(data);
        byte[] signatureBytes = sig.sign();
        System.out.println("Signature:" + new BASE64Encoder().encode(signatureBytes));

        sig.initVerify(keyPair.getPublic());
        sig.update(data);

        System.out.println(sig.verify(signatureBytes));
    }

    private static KeyPair getKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
        kpg.initialize(1024);
        return kpg.genKeyPair();
    }
}

在這里，您需要更改方法 getKeyPair() 以提供您已知的密鑰對。 您可以從 java 密鑰庫 [JKS] 加載它。

你不能只擁有一個任意字節數組作為你的公鑰或私鑰。 它們應該是相關的。

Answer 2

public static String sign(String plainText, PrivateKey privateKey) throws Exception {
    Signature privateSignature = Signature.getInstance("SHA256withRSA");
    privateSignature.initSign(privateKey);
    privateSignature.update(plainText.getBytes(UTF_8));

    byte[] signature = privateSignature.sign();

    return Base64.getEncoder().encodeToString(signature);
}

public static boolean verify(String plainText, String signature, PublicKey publicKey) throws Exception {
    Signature publicSignature = Signature.getInstance("SHA256withRSA");
    publicSignature.initVerify(publicKey);
    publicSignature.update(plainText.getBytes(UTF_8));

    byte[] signatureBytes = Base64.getDecoder().decode(signature);

    return publicSignature.verify(signatureBytes);
}

Answer 3

我使用bouncy-castle對數據進行簽名和驗證。

您應該添加 maven 依賴項：

<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk15on</artifactId>
    <version>1.56</version>
</dependency>
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>1.56</version>
</dependency>

將 RSA 私鑰或公鑰從磁盤文件加載到 Java 對象中

首先，我們需要能夠將 RSA 私鑰或公鑰從磁盤文件加載到 Bouncy Castle 的適當類的 Java 對象中

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.commons.lang3.Validate;
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.util.PrivateKeyFactory;
import org.bouncycastle.crypto.util.PublicKeyFactory;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;

public class KeyUtil {

    public static AsymmetricKeyParameter loadPublicKey(InputStream is) {
        SubjectPublicKeyInfo spki = (SubjectPublicKeyInfo) readPemObject(is);
        try {
            return PublicKeyFactory.createKey(spki);
        } catch (IOException ex) {
            throw new RuntimeException("Cannot create public key object based on input data", ex);
        }
    }

    public static AsymmetricKeyParameter loadPrivateKey(InputStream is) {
        PEMKeyPair keyPair = (PEMKeyPair) readPemObject(is);
        PrivateKeyInfo pki = keyPair.getPrivateKeyInfo();
        try {
            return PrivateKeyFactory.createKey(pki);
        } catch (IOException ex) {
            throw new RuntimeException("Cannot create private key object based on input data", ex);
        }
    }

    private static Object readPemObject(InputStream is) {
        try {
            Validate.notNull(is, "Input data stream cannot be null");
            InputStreamReader isr = new InputStreamReader(is, "UTF-8");
            PEMParser pemParser = new PEMParser(isr);

            Object obj = pemParser.readObject();
            if (obj == null) {
                throw new Exception("No PEM object found");
            }
            return obj;
        } catch (Throwable ex) {
            throw new RuntimeException("Cannot read PEM object from input data", ex);
        }
    }
}

---

創建 RSA 數字簽名

        // GIVEN: InputStream prvKeyInpStream
    AsymmetricKeyParameter privKey = KeyUtil.loadPrivateKey(prvKeyInpStream);

    // GIVEN: byte[] messageBytes = ...
    RSADigestSigner signer = new RSADigestSigner(new SHA512Digest());
    signer.init(true, privKey);
    signer.update(messageBytes, 0, messageBytes.length);

    try {
        byte[] signature = signer.generateSignature();
    } catch (Exception ex) {
        throw new RuntimeException("Cannot generate RSA signature. " + ex.getMessage(), ex);
    }

---

驗證 RSA 數字簽名

// GIVEN: InputStream pubKeyInpStream
AsymmetricKeyParameter publKey = KeyUtil.loadPublicKey(pubKeyInpStream);

// GIVEN: byte[] messageBytes
RSADigestSigner signer = new RSADigestSigner(new SHA512Digest());
signer.init(false, publKey);
signer.update(messageBytes, 0, messageBytes.length);

// GIVEN: byte[] signature - see code sample above
boolean isValidSignature = signer.verifySignature(signature);

Answer 4

public static String sign(String samlResponseString, String keystoreFile, String keyStorePassword, String privateKeyPassword, String alias)
            throws NoSuchAlgorithmException, UnsupportedEncodingException,
            InvalidKeyException, SignatureException {
        PrivateKey pkey=getPrivateKey(  keystoreFile,   keyStorePassword, privateKeyPassword,   alias);
        String signedString = null;
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(pkey);
        signature.update(samlResponseString.getBytes());
        byte[] signatureBytes = signature.sign();
        byte[] encryptedByteValue = Base64.encodeBase64(signatureBytes);
        signedString = new String(encryptedByteValue, "UTF-8");
        System.out.println(signedString);
        return signedString;
    }

Answer 5

您首先必須從字節數組創建一個公鑰

byte publicKeyBytes[] = .... your public key in bytes ... 
KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKeyBytes)); 
PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);

並使用公鑰加密后

String data = "... data to be encrypted ....";
String alg = "RSA/ECB/PKCS1Padding";
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
byte encryptedBytes[] = cipher.doFinal(data.getBytes());

現在只有擁有私鑰的人才能讀取您的數據

@rczajka：publicKey 是一把鑰匙。 您可以使用它來簽署只有所有者（擁有私鑰）才能讀取的東西。