public class RsaUtils {
/**
* 算法名称
*/
private static final String ALGORITHM = "RSA";
/**
* 签名算法 MD5withRSA 或 SHA1WithRSA 等
*/
public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
/**
* 密钥长度默认是1024位:
* 加密的明文最大长度 = 密钥长度 - 11（单位是字节，即byte）
*/
private static final int KEY_SIZE = 1024;
/**
* RSA最大加密明文大小
*/
private static final int MAX_ENCRYPT_BLOCK = 117;
/**
* RSA最大解密密文大小
*/
private static final int MAX_DECRYPT_BLOCK = 128;
/**
* 获取密钥对
*
* @return 密钥对
*/
public static KeyPair getKeyPair() throws Exception {
KeyPairGenerator generator = KeyPairGenerator.getInstance(ALGORITHM);
generator.initialize(KEY_SIZE);
return generator.generateKeyPair();
}
/**
* 私钥字符串转PrivateKey实例
*
* @param privateKey 私钥字符串
* @return
*/
public static PrivateKey getPrivateKey(String privateKey) throws Exception {
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
byte[] decodedKey = Base64.getDecoder().decode(privateKey.getBytes("UTF-8"));// 对私钥进行Base64编码解密
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(decodedKey);
return keyFactory.generatePrivate(keySpec);
}
/**
* 公钥字符串转PublicKey实例
*
* @param publicKey 公钥字符串
* @return
*/
public static PublicKey getPublicKey(String publicKey) throws Exception {
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
byte[] decodedKey = Base64.getDecoder().decode(publicKey.getBytes("UTF-8")); // 对公钥进行Base64编码解密
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(decodedKey);
return keyFactory.generatePublic(keySpec);
}
/**
* 公钥加密
*
* @param data 待加密数据
* @param publicKey 公钥
* @return
*/
public static String encryptByPublicKey(String data, PublicKey publicKey) {
try (
ByteArrayOutputStream out = new ByteArrayOutputStream();
) {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
int inputLen = data.getBytes("UTF-8").length;
int offset = 0;
byte[] cache;
int i = 0;
// 对数据分段加密
while (inputLen - offset > 0) {
if (inputLen - offset > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(data.getBytes("UTF-8"), offset, MAX_ENCRYPT_BLOCK);
} else {
cache = cipher.doFinal(data.getBytes("UTF-8"), offset, inputLen - offset);
}
out.write(cache, 0, cache.length);
i++;
offset = i * MAX_ENCRYPT_BLOCK;
}
byte[] encryptedData = out.toByteArray();
// 获取加密内容使用Base64进行编码加密,并以UTF-8为标准转化成字符串
// 加密后的字符串
//return new String(Base64.encodeBase64String(encryptedData));
return new String(Base64.getEncoder().encode(encryptedData), "UTF-8");
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 私钥解密
*
* @param data 待解密数据
* @param privateKey 私钥
* @return
*/
public static String decryptByPrivateKey(String data, PrivateKey privateKey) {
try (
ByteArrayOutputStream out = new ByteArrayOutputStream();
) {
Cipher cipher = Cipher.getInstance(ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, privateKey);
// 对待解密数据进行Base64编码解密
byte[] dataBytes = Base64.getDecoder().decode(data.getBytes("UTF-8"));
int inputLen = dataBytes.length;
int offset = 0;
byte[] cache;
int i = 0;
// 对数据分段解密
while (inputLen - offset > 0) {
if (inputLen - offset > MAX_DECRYPT_BLOCK) {
cache = cipher.doFinal(dataBytes, offset, MAX_DECRYPT_BLOCK);
} else {
cache = cipher.doFinal(dataBytes, offset, inputLen - offset);
}
out.write(cache, 0, cache.length);
i++;
offset = i * MAX_DECRYPT_BLOCK;
}
byte[] decryptedData = out.toByteArray();
// 解密后的内容
return new String(decryptedData, "UTF-8");
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 私钥签名
*
* @param data 待签名数据
* @param privateKey 私钥
* @return 签名
*/
public static String sign(String data, PrivateKey privateKey) throws Exception {
byte[] keyBytes = privateKey.getEncoded();
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
PrivateKey key = keyFactory.generatePrivate(keySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initSign(key);
signature.update(data.getBytes());
return new String(Base64.getEncoder().encode(signature.sign())); // 对签名内容进行Base64编码加密
}
/**
* 公钥验签
*
* @param srcData 原始字符串
* @param publicKey 公钥
* @param sign 签名
* @return 是否验签通过
*/
public static boolean verify(byte[] srcData, PublicKey publicKey, String sign) throws Exception {
byte[] keyBytes = publicKey.getEncoded();
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
PublicKey key = keyFactory.generatePublic(keySpec);
Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
signature.initVerify(key);
signature.update(srcData);
return signature.verify(Base64.getDecoder().decode(sign));
}
public static void main(String[] args) {
try {
// 生成密钥对
KeyPair keyPair = getKeyPair();
String privateKey = new String(Base64.getEncoder().encode(keyPair.getPrivate().getEncoded()), "UTF-8");
String publicKey = new String(Base64.getEncoder().encode(keyPair.getPublic().getEncoded()), "UTF-8");
System.out.println("私钥:" + privateKey);
System.out.println("公钥:" + publicKey);
// RSA加密
String data = "签名算法可以是NIST标准DSA，使用DSA和SHA-1。 使用SHA-1消息摘要算法的DSA算法可以指定为SHA1withDSA 。 在RSA的情况下，\n" +
"存在对消息多个选择摘要算法，所以签名算法可被指定为，例如， MD2withRSA ， MD5withRSA ，或SHA1withRSA 。 必须指定算法名称，因为没有默认值。";
String encryptData = encryptByPublicKey(data, getPublicKey(publicKey));
System.out.println("加密后内容:" + encryptData);
// RSA解密
String decryptData = decryptByPrivateKey(encryptData, getPrivateKey(privateKey));
System.out.println("解密后内容:" + decryptData);
// RSA签名
String sign = sign(data, getPrivateKey(privateKey));
System.out.println("签名内容:" + sign);
// RSA验签
boolean result = verify(data.getBytes(), getPublicKey(publicKey), sign);
System.out.print("验签结果:" + result);
} catch (Exception e) {
e.printStackTrace();
System.out.print("加密解密异常");
}
}}
