Java怎么使用rsa非对称加密法进行加密

这篇文章主要介绍了Java怎么使用rsa非对称加密法进行加密，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。

公钥与私钥是成对的，一般的，我们认为的是公钥加密、私钥解密、私钥签名、公钥验证，有人说成私钥加密，公钥解密时不对的。

公钥与私钥的生成有多种方式，可以通过程序生成（下文具体实现），可以通过openssl工具：　　

# 生成一个私钥，推荐使用1024位的秘钥，秘钥以pem格式保存到-out参数指定的文件中，采用PKCS1格式openssl genrsa -out rsa.pem 1024# 生成与私钥对应的公钥，生成的是Subject Public Key，一般配合PKCS8格式私钥使用openssl rsa -in rsa.pem -pubout -out rsa.pub

RSA生成公钥与私钥一般有两种格式：PKCS1和PKCS8，上面的命令生成的秘钥是PKCS1格式的，而公钥是Subject Public Key，一般配合PKCS8格式私钥使用，所以就可能会涉及到PKCS1和PKCS8之间的转换：

# PKCS1格式私钥转换为PKCS8格式私钥，私钥直接输出到-out参数指定的文件中openssl pkcs8 -topk8 -inform PEM -in rsa.pem -outform pem -nocrypt -out rsa_pkcs8.pem# PKCS8格式私钥转换为PKCS1格式私钥，私钥直接输出到-out参数指定的文件中openssl rsa -in rsa_pkcs8.pem -out rsa_pkcs1.pem # PKCS1格式公钥转换为PKCS8格式公钥，转换后的内容直接输出openssl rsa -pubin -in rsa.pub -RSAPublicKey_out# PKCS8格式公钥转换为PKCS1格式公钥，转换后的内容直接输出openssl rsa -RSAPublicKey_in -pubout -in rsa.pub

现实中，我们往往从pem、crt、pfx文件获取公私和私钥，crt、pfx的制作可以参考：简单的制作ssl证书，并在nginx和IIS中使用。

Java实现

为简化说明介绍，这里我直接封装了一个工具类，因为要从pem、crt、pfx文件获取公私和私钥，因此引用了一个第三方包：BouncyCastle，可以直接在pom.xml中添加依赖：　　

org.bouncycastlebcprov-jdk15on1.68

简单封装的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());} /*** 随机生成密钥对** @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());// 生成一个密钥对，保存在keyPair中KeyPair keyPair = keyPairGen.generateKeyPair();RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); // 得到私钥RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); // 得到公钥 // 这两个公私钥是PKCS8格式的byte[] publicKeyBytes = publicKey.getEncoded();byte[] privateKeyBytes = privateKey.getEncoded(); if (!usePKCS8) {// 将PSCK8格式公私钥转换为PKCS1格式publicKeyBytes = pkcs8ToPkcs1(false, publicKeyBytes);privateKeyBytes = pkcs8ToPkcs1(true, privateKeyBytes);} return new Object[] { publicKeyBytes, privateKeyBytes };} /*** 从Pem文件读取密钥对** @param reader*            输入流* @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;} /*** 从Pem文件读取密钥** @param isPrivateKey*            是否是私钥* @param buffer*            字节* @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();} /*** 从crt文件读取公钥(pkcs8)** @param crtFileName*            crt文件* @return 公钥*/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();} /*** 从pfx文件读取秘钥对(pkcs8)** @param pfxFileName*            pfx文件* @return 秘钥对*/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 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转Pkcs1** @param isPrivateKey*            是否是私钥转换* @param buffer*            Pkcs1秘钥* @return Pkcs8秘钥* @throws Exception*             加密过程中的异常信息*/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转Pkcs8** @param isPrivateKey*            是否是私钥转换* @param buffer*            Pkcs1秘钥* @return Pkcs8秘钥* @throws Exception*             加密过程中的异常信息*/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公钥** @param usePKCS8*            是否采用PKCS8填充模式* @param publicKey*            公钥* @return 公钥* @throws Exception*             加密过程中的异常信息*/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私钥** @param usePKCS8*            是否采用PKCS8填充模式* @param privateKey*            私钥* @return 私钥* @throws Exception*             解密过程中的异常信息*/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公钥加密** @param value*            加密字符串* @param publicKey*            公钥* @return 密文* @throws Exception*             加密过程中的异常信息*/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格式输出公钥StringBuffer result = new StringBuffer();for (int i = 0; i < buffer.length; i++) {result.append(String.format("x", buffer[i]));}return result.toString();} /*** RSA私钥解密** @param value*            加密字符串* @param privateKey*            私钥* @return 明文* @throws Exception*             解密过程中的异常信息*/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签名** @param value*            加密字符串* @param privateKey*            私钥* @param halg*            加密算法，如MD5, SHA1, SHA256, SHA384, SHA512等* @return 签名* @throws Exception*             签名过程中的异常信息*/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格式输出公钥StringBuffer result = new StringBuffer();for (int i = 0; i < buffer.length; i++) {result.append(String.format("x", buffer[i]));}return result.toString();} /*** RSA签名验证** @param value*            加密字符串* @param publicKey*            公钥* @param halg*            加密算法，如MD5, SHA1, SHA256, SHA384, SHA512等* @return 签名合法则返回true，否则返回false* @throws Exception*             验证过程中的异常信息*/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);} }

生成公钥和私钥：　　

// 生成公私钥Object[] rsaKey = RsaUtil.generateRsaKey(usePKCS8); //usePKCS8=true表示是否成PKCS8格式的公私秘钥,否则乘车PKCS1格式的公私秘钥byte[] publicKey = (byte[]) rsaKey[0];byte[] privateKey = (byte[]) rsaKey[1];

生成秘钥后，需要保存，一般保存到pem文件中：　

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

可以保存到pem文件中，当然也可以从pem文件中读取了：　　

// 从Pem文件读取公私钥，filePath是文件目录byte[] publicKey = RsaUtil.readFromPem(filePath + "rsa.pub");byte[] privateKey = RsaUtil.readFromPem(filePath + "rsa.pem");

还可以从crt证书中读取公钥，而crt文件不包含私钥，因此需要单独获取私钥：　

// 从crt文件读取公钥（crt文件中不包含私钥），filePath是文件目录byte[] publicKey = RsaUtil.readPublicKeyFromCrt(filePath + "demo.crt");byte[] privateKey = RsaUtil.readFromPem(filePath + "demo.key");

pfx文件中包含了公钥和私钥，可以很方便就读取到：　　

// 从pfx文件读取公私钥，filePath是文件目录Object[] rsaKey = RsaUtil.readFromPfx(filePath + "demo.pfx", "123456");byte[] publicKey = (byte[]) rsaKey[0];byte[] privateKey = (byte[]) rsaKey[1];

有时候我们还可能需要进行秘钥的转换：　　

// Pkcs8格式公钥转换为Pkcs1格式公钥publicKey = RsaUtil.pkcs8ToPkcs1(false, publicKey);// Pkcs8格式私钥转换为Pkcs1格式私钥privateKey = RsaUtil.pkcs8ToPkcs1(true, privateKey);// Pkcs1格式公钥转换为Pkcs8格式公钥publicKey = RsaUtil.pkcs1ToPkcs8(false, publicKey);// Pkcs1格式私钥转换为Pkcs8格式私钥privateKey = RsaUtil.pkcs1ToPkcs8(true, privateKey);

有了公钥和私钥，接下就就能实现加密、解密、签名、验证签名等操作了：　　

RSAPublicKey rsaPublicKey = RsaUtil.generatePublicKey(usePKCS8, publicKey);RSAPrivateKey rsaPrivateKey = RsaUtil.generatePrivateKey(usePKCS8, privateKey); String encryptText = RsaUtil.rsaEncrypt(text, rsaPublicKey);System.out.printf("【%s】经过【RSA】加密后：%s\n", text, encryptText); String decryptText = RsaUtil.rsaDecrypt(encryptText, rsaPrivateKey);System.out.printf("【%s】经过【RSA】解密后：%s\n", encryptText, decryptText); String signature = RsaUtil.sign(text, rsaPrivateKey, "MD5");System.out.printf("【%s】经过【RSA】签名后：%s\n", text, signature); boolean result = RsaUtil.verify(text, rsaPublicKey, signature, "MD5");System.out.printf("【%s】的签名【%s】经过【RSA】验证后结果是：" + result, text, signature);

这里完整的demo代码：

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格式的公私秘钥,否则乘车PKCS1格式的公私秘钥String filePath = RsaUtil.class.getClassLoader().getResource("").getPath();System.out.printf("文件路径：%s\n", filePath);// 存放pem,crt,pfx等文件的目录byte[] publicKey, privateKey;// 公钥和私钥 // 生成公私钥Object[] rsaKey = RsaUtil.generateRsaKey(usePKCS8); // usePKCS8=true表示是否成PKCS8格式的公私秘钥,否则乘车PKCS1格式的公私秘钥publicKey = (byte[]) rsaKey[0];privateKey = (byte[]) rsaKey[1];// 从Pem文件读取公私钥，filePath是文件目录// publicKey = RsaUtil.readFromPem(filePath + "rsa.pub");// privateKey = RsaUtil.readFromPem(filePath + "rsa.pem");// 从pfx文件读取公私钥，filePath是文件目录// Object[] rsaKey = RsaUtil.readFromPfx(filePath + "demo.pfx",// "123456");// publicKey = (byte[]) rsaKey[0];// privateKey = (byte[]) rsaKey[1];// 从crt文件读取公钥（crt文件中不包含私钥），filePath是文件目录// publicKey = RsaUtil.readPublicKeyFromCrt(filePath + "demo.crt");// privateKey = RsaUtil.readFromPem(filePath + "demo.key"); // 保存到pem文件，filePath是保存目录RsaUtil.writeToPem(publicKey, false, filePath + "rsa.pub");RsaUtil.writeToPem(privateKey, true, filePath + "rsa.pem"); // Pkcs8格式公钥转换为Pkcs1格式公钥publicKey = RsaUtil.pkcs8ToPkcs1(false, publicKey);// Pkcs8格式私钥转换为Pkcs1格式私钥privateKey = RsaUtil.pkcs8ToPkcs1(true, privateKey);// Pkcs1格式公钥转换为Pkcs8格式公钥publicKey = RsaUtil.pkcs1ToPkcs8(false, publicKey);// Pkcs1格式私钥转换为Pkcs8格式私钥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】经过【RSA】加密后：%s\n", text, encryptText); String decryptText = RsaUtil.rsaDecrypt(encryptText, rsaPrivateKey);System.out.printf("【%s】经过【RSA】解密后：%s\n", encryptText, decryptText); String signature = RsaUtil.sign(text, rsaPrivateKey, "MD5");System.out.printf("【%s】经过【RSA】签名后：%s\n", text, signature); boolean result = RsaUtil.verify(text, rsaPublicKey, signature, "MD5");System.out.printf("【%s】的签名【%s】经过【RSA】验证后结果是：" + result, text, signature); } catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

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