Java 实现RSA非对称加密算法
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公钥与私钥
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，或者使用现成的：https://pan.baidu.com/s/1MJ5YmuZiLBnf-DfNR_6D7A (提取码：c6tj)，密码都是：123456
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：
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk15on</artifactId>
<version>1.68</version>
</dependency>或者去mvn上下载：跳转
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());
}
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 };
}
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;
}
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();
}
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();
}
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() };
}
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();
}
}
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();
}
}
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;
}
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;
}
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("%02x", buffer[i]));
}
return result.toString();
}
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");
}
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("%02x", buffer[i]));
}
return result.toString();
}
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 block
e.printStackTrace();
}
}
}以上就是Java 实现RSA非对称加密算法的详细内容，更多关于Java RSA非对称加密算法的资料请关注编程网其它相关文章！
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