Java如何使用rsa非對稱加密法進(jìn)行加密

公鑰與私鑰是成對的，一般的，我們認(rèn)為的是公鑰加密、私鑰解密、私鑰簽名、公鑰驗證，有人說成私鑰加密，公鑰解密時不對的。

公鑰與私鑰的生成有多種方式，可以通過程序生成（下文具體實現(xiàn)），可以通過openssl工具：　　

    # 生成一個私鑰，推薦使用1024位的秘鑰，秘鑰以pem格式保存到-out參數(shù)指定的文件中，采用PKCS1格式
    openssl genrsa -out rsa.pem 1024
    # 生成與私鑰對應(yīng)的公鑰，生成的是Subject Public Key，一般配合PKCS8格式私鑰使用
    openssl rsa -in rsa.pem -pubout -out rsa.pub  

RSA生成公鑰與私鑰一般有兩種格式：PKCS1和PKCS8，上面的命令生成的秘鑰是PKCS1格式的，而公鑰是Subject Public Key，一般配合PKCS8格式私鑰使用，所以就可能會涉及到PKCS1和PKCS8之間的轉(zhuǎn)換：

    # PKCS1格式私鑰轉(zhuǎn)換為PKCS8格式私鑰，私鑰直接輸出到-out參數(shù)指定的文件中
    openssl pkcs8 -topk8 -inform PEM -in rsa.pem -outform pem -nocrypt -out rsa_pkcs8.pem
    # PKCS8格式私鑰轉(zhuǎn)換為PKCS1格式私鑰，私鑰直接輸出到-out參數(shù)指定的文件中
    openssl rsa -in rsa_pkcs8.pem -out rsa_pkcs1.pem
 
    # PKCS1格式公鑰轉(zhuǎn)換為PKCS8格式公鑰，轉(zhuǎn)換后的內(nèi)容直接輸出
    openssl rsa -pubin -in rsa.pub -RSAPublicKey_out
    # PKCS8格式公鑰轉(zhuǎn)換為PKCS1格式公鑰，轉(zhuǎn)換后的內(nèi)容直接輸出
    openssl rsa -RSAPublicKey_in -pubout -in rsa.pub

現(xiàn)實中，我們往往從pem、crt、pfx文件獲取公私和私鑰，crt、pfx的制作可以參考：簡單的制作ssl證書，并在nginx和IIS中使用。

Java實現(xiàn)

為簡化說明介紹，這里我直接封裝了一個工具類，因為要從pem、crt、pfx文件獲取公私和私鑰，因此引用了一個第三方包：BouncyCastle，可以直接在pom.xml中添加依賴：　　

    <dependency>
        <groupId>org.bouncycastle</groupId>
        <artifactId>bcprov-jdk15on</artifactId>
        <version>1.68</version>
    </dependency>

簡單封裝的RsaUtil.java:　　

import java.io.FileInputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Security;
import java.security.Signature;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Enumeration;
 
import javax.crypto.Cipher;
 
import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.ASN1Primitive;
import org.bouncycastle.asn1.DLSequence;
import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.io.pem.PemObject;
import org.bouncycastle.util.io.pem.PemReader;
import org.bouncycastle.util.io.pem.PemWriter;
 
public class RsaUtil {
 
    static {
        Security.addProvider(new BouncyCastleProvider());
    }
 
    /**
     * 隨機(jī)生成密鑰對
     *
     * @param usePKCS8
     *            是否采用PKCS8填充模式
     */
    public static Object[] generateRsaKey(boolean usePKCS8) throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA", BouncyCastleProvider.PROVIDER_NAME);
        // 初始化
        keyPairGen.initialize(1024, new SecureRandom());
        // 生成一個密鑰對，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); // 得到私鑰
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); // 得到公鑰
 
        // 這兩個公私鑰是PKCS8格式的
        byte[] publicKeyBytes = publicKey.getEncoded();
        byte[] privateKeyBytes = privateKey.getEncoded();
 
        if (!usePKCS8) {
            // 將PSCK8格式公私鑰轉(zhuǎn)換為PKCS1格式
            publicKeyBytes = pkcs8ToPkcs1(false, publicKeyBytes);
            privateKeyBytes = pkcs8ToPkcs1(true, privateKeyBytes);
        }
 
        return new Object[] { publicKeyBytes, privateKeyBytes };
    }
 
    /**
     * 從Pem文件讀取密鑰對
     *
     * @param reader
     *            輸入流
     * @param pemFileName
     *            pem文件
     */
    public static byte[] readFromPem(String pemFileName) throws Exception {
        PemReader pemReader = new PemReader(new FileReader(pemFileName));
        PemObject pemObject = pemReader.readPemObject();
        byte[] publicKey = pemObject.getContent();
        pemReader.close();
        return publicKey;
    }
 
    /**
     * 從Pem文件讀取密鑰
     *
     * @param isPrivateKey
     *            是否是私鑰
     * @param buffer
     *            字節(jié)
     * @param pemFileName
     *            pem文件
     */
    public static void writeToPem(byte[] buffer, boolean isPrivateKey, String pemFileName) throws Exception {
 
        PemObject pemObject = new PemObject(isPrivateKey ? "RSA PRIVATE KEY" : "RSA PUBLIC KEY", buffer);
        FileWriter fileWriter = new FileWriter(pemFileName);
        PemWriter pemWriter = new PemWriter(fileWriter);
        pemWriter.writeObject(pemObject);
        pemWriter.close();
    }
 
    /**
     * 從crt文件讀取公鑰(pkcs8)
     *
     * @param crtFileName
     *            crt文件
     * @return 公鑰
     */
    public static byte[] readPublicKeyFromCrt(String crtFileName) throws Exception {
        CertificateFactory cf = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) cf.generateCertificate(new FileInputStream(crtFileName));
 
        PublicKey publicKey = cert.getPublicKey();
        return publicKey.getEncoded();
    }
 
    /**
     * 從pfx文件讀取秘鑰對(pkcs8)
     *
     * @param pfxFileName
     *            pfx文件
     * @return 秘鑰對
     */
    public static Object[] readFromPfx(String pfxFileName, String password) throws Exception {
        KeyStore keystore = KeyStore.getInstance("PKCS12");
        char[] passwordChars = null;
        if (password == null || password.equals("")) {
            passwordChars = null;
        } else {
            passwordChars = password.toCharArray();
        }
        keystore.load(new FileInputStream(pfxFileName), passwordChars);
        Enumeration<String> enums = keystore.aliases();
 
        PrivateKey privateKey = null;
        Certificate certificate = null;
        while (enums.hasMoreElements()) {
            String alias = enums.nextElement();
            System.out.println(alias);
            if (keystore.isKeyEntry(alias)) {
                privateKey = (PrivateKey) keystore.getKey(alias, passwordChars);
                certificate = keystore.getCertificate(alias);
            }
            if (privateKey != null && certificate != null)
                break;
        }
        if (privateKey == null || certificate == null) {
            throw new Exception("fail to read key from pfx");
        }
 
        PublicKey publicKey = certificate.getPublicKey();
        return new Object[] { publicKey.getEncoded(), privateKey.getEncoded() };
    }
 
    /**
     * Pkcs8轉(zhuǎn)Pkcs1
     *
     * @param isPrivateKey
     *            是否是私鑰轉(zhuǎn)換
     * @param buffer
     *            Pkcs1秘鑰
     * @return Pkcs8秘鑰
     * @throws Exception
     *             加密過程中的異常信息
     */
    public static byte[] pkcs8ToPkcs1(boolean isPrivateKey, byte[] buffer) throws Exception {
        if (isPrivateKey) {
            PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(buffer);
            return privateKeyInfo.parsePrivateKey().toASN1Primitive().getEncoded();
        } else {
            SubjectPublicKeyInfo subjectPublicKeyInfo = SubjectPublicKeyInfo.getInstance(buffer);
            return subjectPublicKeyInfo.parsePublicKey().toASN1Primitive().getEncoded();
        }
    }
 
    /**
     * Pkcs1轉(zhuǎn)Pkcs8
     *
     * @param isPrivateKey
     *            是否是私鑰轉(zhuǎn)換
     * @param buffer
     *            Pkcs1秘鑰
     * @return Pkcs8秘鑰
     * @throws Exception
     *             加密過程中的異常信息
     */
    public static byte[] pkcs1ToPkcs8(boolean isPrivateKey, byte[] buffer) throws Exception {
        AlgorithmIdentifier algorithmIdentifier = new AlgorithmIdentifier(PKCSObjectIdentifiers.rsaEncryption);
        ASN1Primitive asn1Primitive = ASN1Primitive.fromByteArray(buffer);
        if (isPrivateKey) {
            PrivateKeyInfo privateKeyInfo = new PrivateKeyInfo(algorithmIdentifier, asn1Primitive);
            return privateKeyInfo.getEncoded();
        } else {
            SubjectPublicKeyInfo subjectPublicKeyInfo = new SubjectPublicKeyInfo(algorithmIdentifier, asn1Primitive);
            return subjectPublicKeyInfo.getEncoded();
        }
    }
 
    /**
     * RSA公鑰
     *
     * @param usePKCS8
     *            是否采用PKCS8填充模式
     * @param publicKey
     *            公鑰
     * @return 公鑰
     * @throws Exception
     *             加密過程中的異常信息
     */
    public static RSAPublicKey generatePublicKey(boolean usePKCS8, byte[] publicKey) throws Exception {
        KeySpec keySpec;
        if (usePKCS8) {
            // PKCS8填充
            keySpec = new X509EncodedKeySpec(publicKey);
        } else {
            // PKCS1填充
            DLSequence sequence = (DLSequence) ASN1Primitive.fromByteArray(publicKey);
            BigInteger v1 = ((ASN1Integer) sequence.getObjectAt(0)).getValue();
            BigInteger v2 = ((ASN1Integer) sequence.getObjectAt(1)).getValue();
            keySpec = new RSAPublicKeySpec(v1, v2);
        }
 
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA", BouncyCastleProvider.PROVIDER_NAME).generatePublic(keySpec);
        return pubKey;
    }
 
    /**
     * RSA私鑰
     *
     * @param usePKCS8
     *            是否采用PKCS8填充模式
     * @param privateKey
     *            私鑰
     * @return 私鑰
     * @throws Exception
     *             解密過程中的異常信息
     */
    public static RSAPrivateKey generatePrivateKey(boolean usePKCS8, byte[] privateKey) throws Exception {
        KeySpec keySpec;
        if (usePKCS8) {
            // PKCS8填充
            keySpec = new PKCS8EncodedKeySpec(privateKey);
        } else {
            // PKCS1填充
            DLSequence sequence = (DLSequence) ASN1Primitive.fromByteArray(privateKey);
            // BigInteger v1= ((ASN1Integer)sequence.getObjectAt(0)).getValue();
            BigInteger v2 = ((ASN1Integer) sequence.getObjectAt(1)).getValue();
            BigInteger v3 = ((ASN1Integer) sequence.getObjectAt(2)).getValue();
            BigInteger v4 = ((ASN1Integer) sequence.getObjectAt(3)).getValue();
            BigInteger v5 = ((ASN1Integer) sequence.getObjectAt(4)).getValue();
            BigInteger v6 = ((ASN1Integer) sequence.getObjectAt(5)).getValue();
            BigInteger v7 = ((ASN1Integer) sequence.getObjectAt(6)).getValue();
            BigInteger v8 = ((ASN1Integer) sequence.getObjectAt(7)).getValue();
            BigInteger v9 = ((ASN1Integer) sequence.getObjectAt(8)).getValue();
            keySpec = new RSAPrivateCrtKeySpec(v2, v3, v4, v5, v6, v7, v8, v9);
        }
 
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA", BouncyCastleProvider.PROVIDER_NAME).generatePrivate(keySpec);
        return priKey;
    }
 
    /**
     * RSA公鑰加密
     *
     * @param value
     *            加密字符串
     * @param publicKey
     *            公鑰
     * @return 密文
     * @throws Exception
     *             加密過程中的異常信息
     */
    public static String rsaEncrypt(String value, RSAPublicKey publicKey) throws Exception {
        if (value == null || value.length() == 0)
            return "";
 
        // RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] buffer = cipher.doFinal(value.getBytes("utf-8"));
 
        // 使用hex格式輸出公鑰
        StringBuffer result = new StringBuffer();
        for (int i = 0; i < buffer.length; i++) {
            result.append(String.format("%02x", buffer[i]));
        }
        return result.toString();
    }
 
    /**
     * RSA私鑰解密
     *
     * @param value
     *            加密字符串
     * @param privateKey
     *            私鑰
     * @return 明文
     * @throws Exception
     *             解密過程中的異常信息
     */
    public static String rsaDecrypt(String value, RSAPrivateKey privateKey) throws Exception {
        if (value == null || value.length() == 0)
            return "";
 
        byte[] buffer = new byte[value.length() / 2];
        for (int i = 0; i < buffer.length; i++) {
            buffer[i] = (byte) Integer.parseInt(value.substring(i * 2, i * 2 + 2), 16);
        }
 
        // RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        buffer = cipher.doFinal(buffer);
        return new String(buffer, "utf-8");
    }
 
    /**
     * RSA簽名
     *
     * @param value
     *            加密字符串
     * @param privateKey
     *            私鑰
     * @param halg
     *            加密算法，如MD5, SHA1, SHA256, SHA384, SHA512等
     * @return 簽名
     * @throws Exception
     *             簽名過程中的異常信息
     */
    public static String sign(String value, RSAPrivateKey privateKey, String halg) throws Exception {
 
        Signature s = Signature.getInstance(halg.toUpperCase().endsWith("WithRSA") ? halg : (halg + "WithRSA"));
 
        s.initSign(privateKey);
        s.update(value.getBytes("utf-8"));
 
        byte[] buffer = s.sign();
 
        // 使用hex格式輸出公鑰
        StringBuffer result = new StringBuffer();
        for (int i = 0; i < buffer.length; i++) {
            result.append(String.format("%02x", buffer[i]));
        }
        return result.toString();
    }
 
    /**
     * RSA簽名驗證
     *
     * @param value
     *            加密字符串
     * @param publicKey
     *            公鑰
     * @param halg
     *            加密算法，如MD5, SHA1, SHA256, SHA384, SHA512等
     * @return 簽名合法則返回true，否則返回false
     * @throws Exception
     *             驗證過程中的異常信息
     */
    public static boolean verify(String value, RSAPublicKey publicKey, String signature, String halg) throws Exception {
        Signature s = Signature.getInstance(halg.toUpperCase().endsWith("WithRSA") ? halg : (halg + "WithRSA"));
        s.initVerify(publicKey);
        s.update(value.getBytes("utf-8"));
 
        byte[] buffer = new byte[signature.length() / 2];
        for (int i = 0; i < buffer.length; i++) {
            buffer[i] = (byte) Integer.parseInt(signature.substring(i * 2, i * 2 + 2), 16);
        }
 
        return s.verify(buffer);
    }
 
}

生成公鑰和私鑰：　　

    // 生成公私鑰
    Object[] rsaKey = RsaUtil.generateRsaKey(usePKCS8); //usePKCS8=true表示是否成PKCS8格式的公私秘鑰,否則乘車PKCS1格式的公私秘鑰
    byte[] publicKey = (byte[]) rsaKey[0];
    byte[] privateKey = (byte[]) rsaKey[1];

生成秘鑰后，需要保存，一般保存到pem文件中：　

    // 保存到pem文件，filePath是保存目錄
    RsaUtil.writeToPem(publicKey, false, filePath + "rsa.pub");
    RsaUtil.writeToPem(privateKey, true, filePath + "rsa.pem");

可以保存到pem文件中，當(dāng)然也可以從pem文件中讀取了：　　

    // 從Pem文件讀取公私鑰，filePath是文件目錄
    byte[] publicKey = RsaUtil.readFromPem(filePath + "rsa.pub");
    byte[] privateKey = RsaUtil.readFromPem(filePath + "rsa.pem");

還可以從crt證書中讀取公鑰，而crt文件不包含私鑰，因此需要單獨(dú)獲取私鑰：　

    // 從crt文件讀取公鑰（crt文件中不包含私鑰），filePath是文件目錄
    byte[] publicKey = RsaUtil.readPublicKeyFromCrt(filePath + "demo.crt");
    byte[] privateKey = RsaUtil.readFromPem(filePath + "demo.key");

pfx文件中包含了公鑰和私鑰，可以很方便就讀取到：　　

    // 從pfx文件讀取公私鑰，filePath是文件目錄
    Object[] rsaKey = RsaUtil.readFromPfx(filePath + "demo.pfx", "123456");
    byte[] publicKey = (byte[]) rsaKey[0];
    byte[] privateKey = (byte[]) rsaKey[1];

有時候我們還可能需要進(jìn)行秘鑰的轉(zhuǎn)換：　　

    // Pkcs8格式公鑰轉(zhuǎn)換為Pkcs1格式公鑰
    publicKey = RsaUtil.pkcs8ToPkcs1(false, publicKey);
    // Pkcs8格式私鑰轉(zhuǎn)換為Pkcs1格式私鑰
    privateKey = RsaUtil.pkcs8ToPkcs1(true, privateKey);
    // Pkcs1格式公鑰轉(zhuǎn)換為Pkcs8格式公鑰
    publicKey = RsaUtil.pkcs1ToPkcs8(false, publicKey);
    // Pkcs1格式私鑰轉(zhuǎn)換為Pkcs8格式私鑰
    privateKey = RsaUtil.pkcs1ToPkcs8(true, privateKey);

有了公鑰和私鑰，接下就就能實現(xiàn)加密、解密、簽名、驗證簽名等操作了：　　

    RSAPublicKey rsaPublicKey = RsaUtil.generatePublicKey(usePKCS8, publicKey);
    RSAPrivateKey rsaPrivateKey = RsaUtil.generatePrivateKey(usePKCS8, privateKey);
 
    String encryptText = RsaUtil.rsaEncrypt(text, rsaPublicKey);
    System.out.printf("【%s】經(jīng)過【RSA】加密后：%s\n", text, encryptText);
 
    String decryptText = RsaUtil.rsaDecrypt(encryptText, rsaPrivateKey);
    System.out.printf("【%s】經(jīng)過【RSA】解密后：%s\n", encryptText, decryptText);
 
    String signature = RsaUtil.sign(text, rsaPrivateKey, "MD5");
    System.out.printf("【%s】經(jīng)過【RSA】簽名后：%s\n", text, signature);
 
    boolean result = RsaUtil.verify(text, rsaPublicKey, signature, "MD5");
    System.out.printf("【%s】的簽名【%s】經(jīng)過【RSA】驗證后結(jié)果是：" + result, text, signature);

這里完整的demo代碼：

    import java.security.interfaces.RSAPrivateKey;
    import java.security.interfaces.RSAPublicKey;
 
    public class RsaMain {
 
        public static void main(String[] args) {
            try {
                String text = "上山打老虎";
                boolean usePKCS8 = true; // usePKCS8=true表示是否成PKCS8格式的公私秘鑰,否則乘車PKCS1格式的公私秘鑰
                String filePath = RsaUtil.class.getClassLoader().getResource("").getPath();
                System.out.printf("文件路徑：%s\n", filePath);// 存放pem,crt,pfx等文件的目錄
                byte[] publicKey, privateKey;// 公鑰和私鑰
 
                // 生成公私鑰
                Object[] rsaKey = RsaUtil.generateRsaKey(usePKCS8); // usePKCS8=true表示是否成PKCS8格式的公私秘鑰,否則乘車PKCS1格式的公私秘鑰
                publicKey = (byte[]) rsaKey[0];
                privateKey = (byte[]) rsaKey[1];
                // 從Pem文件讀取公私鑰，filePath是文件目錄
                // publicKey = RsaUtil.readFromPem(filePath + "rsa.pub");
                // privateKey = RsaUtil.readFromPem(filePath + "rsa.pem");
                // 從pfx文件讀取公私鑰，filePath是文件目錄
                // Object[] rsaKey = RsaUtil.readFromPfx(filePath + "demo.pfx",
                // "123456");
                // publicKey = (byte[]) rsaKey[0];
                // privateKey = (byte[]) rsaKey[1];
                // 從crt文件讀取公鑰（crt文件中不包含私鑰），filePath是文件目錄
                // publicKey = RsaUtil.readPublicKeyFromCrt(filePath + "demo.crt");
                // privateKey = RsaUtil.readFromPem(filePath + "demo.key");
 
                // 保存到pem文件，filePath是保存目錄
                RsaUtil.writeToPem(publicKey, false, filePath + "rsa.pub");
                RsaUtil.writeToPem(privateKey, true, filePath + "rsa.pem");
 
                // Pkcs8格式公鑰轉(zhuǎn)換為Pkcs1格式公鑰
                publicKey = RsaUtil.pkcs8ToPkcs1(false, publicKey);
                // Pkcs8格式私鑰轉(zhuǎn)換為Pkcs1格式私鑰
                privateKey = RsaUtil.pkcs8ToPkcs1(true, privateKey);
                // Pkcs1格式公鑰轉(zhuǎn)換為Pkcs8格式公鑰
                publicKey = RsaUtil.pkcs1ToPkcs8(false, publicKey);
                // Pkcs1格式私鑰轉(zhuǎn)換為Pkcs8格式私鑰
                privateKey = RsaUtil.pkcs1ToPkcs8(true, privateKey);
 
                RSAPublicKey rsaPublicKey = RsaUtil.generatePublicKey(usePKCS8, publicKey);
                RSAPrivateKey rsaPrivateKey = RsaUtil.generatePrivateKey(usePKCS8, privateKey);
 
                String encryptText = RsaUtil.rsaEncrypt(text, rsaPublicKey);
                System.out.printf("【%s】經(jīng)過【RSA】加密后：%s\n", text, encryptText);
 
                String decryptText = RsaUtil.rsaDecrypt(encryptText, rsaPrivateKey);
                System.out.printf("【%s】經(jīng)過【RSA】解密后：%s\n", encryptText, decryptText);
 
                String signature = RsaUtil.sign(text, rsaPrivateKey, "MD5");
                System.out.printf("【%s】經(jīng)過【RSA】簽名后：%s\n", text, signature);
 
                boolean result = RsaUtil.verify(text, rsaPublicKey, signature, "MD5");
                System.out.printf("【%s】的簽名【%s】經(jīng)過【RSA】驗證后結(jié)果是：" + result, text, signature);
 
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

以上就是Java 實現(xiàn)RSA非對稱加密算法的詳細(xì)內(nèi)容。