安卓逆向 -- 算法基础(RSA)

1337163122 · 发表于 2021-8-29 16:47:20

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#安卓逆向#算法基础#RSA
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一、非对称加密算法
1、对称加密算法中，加密和解密用到的密钥是一样的，而非对称加密算法，加密和解密的密钥是不一样的。非对称加密算法有公钥和私钥，公钥加密私钥解密。加密处理安全，但是性能极差，单次加密长度有限制。
2、填充方式：pkcs1padding，明文最大字节数为密钥字节数-11密文与密钥等长；NoPadding，明文最大字节数为密钥字节数，密文与密钥等长。
二、密钥对生成
密钥不是随便给的，需要特殊算法生成，可以在线生成：http://web.chacuo.net/netrsakeypair

三、Java版

public static String pubkey="MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQClAtuZCNosKZMNyn90bCQl3qVdMniH4y9NGIcWNFBdmh" +
"DF3YeWEB+wLeGMw2h5PQtwJBz0G1mhRhCtF+Yx/DuuxDrYjjTsj9k4V5pgkpUbF+1z0C1sJDs6z/CPRVwRdwwJVymxdNfC" +
"mLZ9QtT6yMfZdZqIsh1fHHw599IMz3/9fQIDAQAB";
public static String prikey="MIICeAIBADANBgkqhkiG9w0BAQEFAASCAmIwggJeAgEAAoGBAKUC25kI2iwpkw3Kf3RsJCXepV0yeIfjL" +
"00YhxY0UF2aEMXdh5YQH7At4YzDaHk9C3AkHPQbWaFGEK0X5jH8O67EOtiONOyP2ThXmmCSlRsX7XPQLWwkOzr" +
"P8I9FXBF3DAlXKbF018KYtn1C1PrIx9l1moiyHV8cfDn30gzPf/19AgMBAAECgYBsdzdwHdCDrQRb0Vr8ZUVRm" +
"0upuk5eTGjATbomT1bwYCBcX+ULMCgUP+R+Cci3wPeuzB44G25MQ2kczpPjEYEMrnf5BlzXB5QkOaWPVIETEJF" +
"lDIIUonvpvb8if1C6/GTqc6iQQEbMmFcV4DmeI282o/56SQp6ia9lPfIanNmS5QJBANq7YzIpCGOEC7Aq0o8es" +
"WTMp4xT/hYNH5hYexy9qIjTNB85jpxHtctHwnXD04YXky22hX/owVPFMSeNyxuYgcMCQQDBIEkFIZdbZZhMjSY" +
"c/UtCD+G2XKWe+r5Lkt8hZCo60P5KRta4+kYzcEwYVSn2zMNFCZwGKR0xGLyWDp2d5E+/AkEAnf4AlrjA0HEOqD" +
"8mPC6lX/PbiicZPwBXtAklVAtCcyJrYaqHcibyD1VUBxBd91uL+db+8vdCvamP6cwny1ULVQJBAIVw7GNaQX3KZ" +
"gBG6xXOwohj9t6Nh3ag5InNctVco30+WOYzqjvn2kfCiSGq/rLj6uyx5hevotcAs5WvhaLKVXsCQQDXdkUSR5p8" +
"NYRRv3+ovAnZVilMo+pAfaG+/SVphKoF43Mu2P3On+d6VzplLiRNsgGsLZB4t/sCyChdex3XwMrU";
public static PublicKey getPublickKey(String key)throws Exception{
byte[] keyBytes= new BASE64Decoder().decodeBuffer(key);
X509EncodedKeySpec keys = new X509EncodedKeySpec(keyBytes);//实例化key
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey publicKey = keyFactory.generatePublic(keys);
return publicKey;
}
public static PrivateKey getPrivatekey(String key)throws Exception{
byte[] bytes = new BASE64Decoder().decodeBuffer(key);
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(bytes);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
return privateKey;
}
public static byte[] encrypt(byte[] enstr)throws Exception{
PublicKey publickKey = getPublickKey(pubkey);
Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");
cipher.init(Cipher.ENCRYPT_MODE,publickKey);
byte[] bytes = cipher.doFinal(enstr);
return bytes;
}
public static byte[] decrypt(byte[] destr)throws Exception{
PrivateKey privatekey = getPrivatekey(prikey);
Cipher cipht = Cipher.getInstance("RSA/ECB/NoPadding");
cipht.init(Cipher.DECRYPT_MODE,privatekey);
byte[] bytes= cipht.doFinal(destr);
return bytes;
}
public static void main(String[] args) throws Exception{
System.out.println("逆向有你");
String bs= "逆向有你a";
byte[] enby = encrypt(bs.getBytes(StandardCharsets.UTF_8));
System.out.println("RSA加密（字节）："+Arrays.toString(enby));
System.out.println("RSA加密（Hex）："+bytes2HexString(enby));
System.out.println("RSA加密（Base64）："+Base64.getEncoder().encodeToString(enby));
byte[] deby = decrypt(enby);
System.out.println("RSA解密（字节）："+new String(deby));
}
运行结果：
RSA加密（字节）：[-95, 75, -84, -31, 54, 59, 9, -101, 58, 3, -127, -23, -108, -41, 67, 52, -17, -82, -67, -15, 21, -113, 20, 0, 93, 31, -81, -66, 86, 97, 41, 12, 24, -72, 18, -33, -102, -72, -3, -106, 13, 81, 15, 39, -87, -16, -40, -84, 123, -46, 108, 58, -73, 31, -52, -39, 66, 24, 57, 12, -43, -107, -65, 98, 33, -28, 120, 17, 1, -62, 63, 108, -46, 57, 43, -40, 113, -85, 15, 25, 29, 123, -68, 18, 27, 96, -27, -23, -1, 8, 119, 45, -10, 48, -53, -42, 63, 5, -34, 41, 83, -101, 74, -104, -16, 79, 93, 71, 105, -52, -16, -52, 5, -85, -52, -83, -11, 93, 7, -39, 23, 106, -53, -57, 42, -111, 68, -71]
RSA加密（Hex）：A14BACE1363B099B3A0381E994D74334EFAEBDF1158F14005D1FAFBE5661290C18B812DF9AB8FD960D510F27A9F0D8AC7BD26C3AB71FCCD94218390CD595BF6221E4781101C23F6CD2392BD871AB0F191D7BBC121B60E5E9FF08772DF630CBD63F05DE29539B4A98F04F5D4769CCF0CC05ABCCADF55D07D9176ACBC72A9144B9
RSA加密（Base64）：oUus4TY7CZs6A4HplNdDNO+uvfEVjxQAXR+vvlZhKQwYuBLfmrj9lg1RDyep8Nise9JsOrcfzNlCGDkM1ZW/YiHkeBEBwj9s0jkr2HGrDxkde7wSG2Dl6f8Idy32MMvWPwXeKVObSpjwT11HaczwzAWrzK31XQfZF2rLxyqRRLk=
RSA解密（字节）：逆向有你a

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四、JS版

var JSEncrypt = JSEncryptExports.JSEncrypt;
function getEncrypt(password, publickey){
var jsEncrypt = new JSEncrypt();
jsEncrypt.setPublicKey(publickey);
return jsEncrypt.encrypt(password);//默认返回Base64格式
}
var publicKeyBase64 ="MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQClAtuZCNosKZMNyn90bCQl3qVdMniH4y9NGIcWNFBdmhDF3YeWEB+wLeGMw2h5PQtwJBz0G1mhRhCtF+Yx/DuuxDrYjjTsj9k4V5pgkpUbF+1z0C1sJDs6z/CPRVwRdwwJVymxdNfCmLZ9QtT6yMfZdZqIsh1fHHw599IMz3/9fQIDAQAB";
console.log(getEncrypt("逆向有你", publicKeyBase64));

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禁止非法，后果自负
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