1. 首先你要拥有一对公钥、私钥；
```
pubKeyStr = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC1gr+rIfYlaNUNLiFsK/Knb54nQrCRTRMOdujTwkpqKLo4pNYj2StmryWETeFxOCFtCt/7ixTUrU2RGGjkIOlYC3144h0dJKDtPXw9+mFyW1VwWvtfoiSUeKTEbz1tSHghEcdEvVq6qlSQukiLAEZabiwfEE30TQ6g979X6YXhnQIDAQAB";
priKeyStr = "MIICeQIBADANBgkqhkiG9w0BAQEFAASCAmMwggJfAgEAAoGBALWCv6sh9iVo1Q0uIWwr8qdvnidCsJFNEw526NPCSmooujik1iPZK2avJYRN4XE4IW0K3/uLFNStTZEYaOQg6VgLfXjiHR0koO09fD36YXJbVXBa+1+iJJR4pMRvPW1IeCERx0S9WrqqVJC6SIsARlpuLB8QTfRNDqD3v1fpheGdAgMBAAECgYEArmr1w3zfCxOxpvitJUUV589aKl/rS7TEmyGomdQZrel1CPlczRXinsmvQ3OTLzjA5geNNCpx2eyunL7YDF+T2WgcvpPlM+TUrBnTI9gKYwLXiWPuWou8oZolHaTuQQuLfnJTZ+6cYjHA3S4xnrJaEvvs8xgy6/UAJWXUpm/dQAECQQDlW9LPOrWaaVFuZqftVTwhTjhVmBZ/AeuXcmmmF2KBGaujbXJuVHVE5rzW9/6TQoWinuK4J/UOLcFl3VTTEPgZAkEAypggJwgYq3uz0KX8YScHV/gUZa56l5gRofMrIpiek4uvt2JM1kqgIq9T9PIOnv7dz7buRk2GXi3GLgEuhDr2JQJBAJPAypZ7QMBfdnkDosyOqzTdegcR+fQJ3aZrq0m3KNr4GY0nlZ8jw4QGjMKDcjmVkhdH+dAe1Ywzx7ICmoF6HgkCQQCTo+lKiIvx7GROWahi5J5lbVTwBQcyEpBHBX8Z5z8pJ1MWwXxdbmTk4gC9MOmW1QWwqg9bDIQvfgw+2n2bv5xBAkEAhUaiDfOywrIB3VUZWTqeIlVfqXHd8a9AcellTgIjK8WIu9gNGIfkWUVoVeOq0GCFTVqwO5tlac+oeDHCCimLyQ==";
```
生成方法略；
2. js中加密
* 获取公钥的Exponent/Modulus 供js中使用
```
publicKey.getPublicExponent().toString(16);
publicKey.getModulus().toString(16);
```
* 依赖包地址
引入依赖文件后
```
var rsa_m = "b582bfab21f62568d50d2e216c2bf2a76f9e2742b0914d130e76e8d3c24a6a28ba38a4d623d92b66af25844de17138216d0adffb8b14d4ad4d911868e420e9580b7d78e21d1d24a0ed3d7c3dfa61725b55705afb5fa2249478a4c46f3d6d48782111c744bd5abaaa5490ba488b00465a6e2c1f104df44d0ea0f7bf57e985e19d";
var rsa_e = "10001";
setMaxDigits(131); //131 => n的十六进制位数/2+3
var key = new RSAKeyPair(rsa_e, ‘‘, rsa_m); //e,m是从Java代码中获取的
var password = "123456";
password = encryptedString(key, password); //不支持汉字
// 将password传递到后台，在后台使用Java解密
```
3. java 解密
因为js加密时使用的是nopadding模式（每次加密结果一样），而java中默认是padding15，每次加密结果不一样，所以要依赖第三方包来解密
/*
// http://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk15on
compile group: ‘org.bouncycastle‘, name: ‘bcprov-jdk15on‘, version: ‘1.54‘
*/
```
RSAUtil.decryptJSRsa(password);
```
java 代码工具类:
```
package com.wch.encrypt;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import javax.crypto.Cipher;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Hex;
import com.netfinworks.util.RSA;
/**
* RSA 工具类。提供加密，解密，生成密钥对等方法。 需要bcprov-jdk16-140.jar包。
* js依赖http://www.ohdave.com/rsa/
* // http://mvnrepository.com/artifact/org.bouncycastle/bcprov-jdk15on
compile group: ‘org.bouncycastle‘, name: ‘bcprov-jdk15on‘, version: ‘1.54‘
*/
public class RSAUtil {
private static final String pubKeyStr = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC1gr+rIfYlaNUNLiFsK/Knb54nQrCRTRMOdujTwkpqKLo4pNYj2StmryWETeFxOCFtCt/7ixTUrU2RGGjkIOlYC3144h0dJKDtPXw9+mFyW1VwWvtfoiSUeKTEbz1tSHghEcdEvVq6qlSQukiLAEZabiwfEE30TQ6g979X6YXhnQIDAQAB";
private static final String priKeyStr = "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";
/**
* 解密js加密的rsa
*
* @param str
* js加密后的字符串;
* js加密参考http://blog.csdn.net/songxiaobing/article/details
* /17505237
* @return
*/
public static String decryptJSRsa(String str) {
PrivateKey privateKey;
try {
privateKey = RSA.getPrivateKey(priKeyStr);
Cipher cipher = Cipher.getInstance("RSA/NONE/NoPadding",
new BouncyCastleProvider());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
StringBuilder sb = new StringBuilder(new String(cipher.doFinal(Hex
.decode(str))));
return sb.reverse().toString();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 原生加解密代码
*
* @throws Exception
*/
public static void rsaTest() throws Exception {
KeyFactory factory = KeyFactory.getInstance("RSA",
new BouncyCastleProvider());
byte[] bytes = Base64.getDecoder().decode(pubKeyStr);
X509EncodedKeySpec spec = new X509EncodedKeySpec(bytes);
RSAPublicKey publicKey = (RSAPublicKey) factory.generatePublic(spec);
System.out.println(publicKey.getPublicExponent().toString(16));
System.out.println(publicKey.getModulus().toString(16));
byte[] pirvateBytes = Base64.getDecoder().decode(priKeyStr);
PKCS8EncodedKeySpec privateSpec = new PKCS8EncodedKeySpec(pirvateBytes);
PrivateKey privateKey = factory.generatePrivate(privateSpec);
byte[] encode = RSA.encrypt("wch".getBytes(), privateKey);
System.out.println(Base64.getEncoder().encodeToString(encode));
System.out.println(new String(RSA.decrypt(encode, publicKey)));
byte[] publicEncode = RSA.encrypt("pubic".getBytes(), publicKey);
System.out.println(Base64.getEncoder().encodeToString(publicEncode));
System.out.println(new String(RSA.decrypt(publicEncode, privateKey)));
byte[] sign = RSA.sign("wch".getBytes(), privateKey);
System.out.println(Base64.getEncoder().encodeToString(sign));
System.out.println(RSA.verify("wch".getBytes(), sign, publicKey));
}
public static void main(String[] args) throws Exception {
rsaTest();
}
}
```