我目前正在使用Java进行RSA加密，我必须使用私有和公共模数进行加密。我目前有以下内容：
private void createPublicKey() throws NoSuchAlgorithmException, InvalidKeySpecException {
String publicModulus = "d2c34017ef94f8ab6696dae66e3c0d1ad186bbd9ce4461b68d7cd017c15bda174045bfef36fbf048" +
"73cfd6d09e3806af3949f99c3e09d6d3c37f6398d8c63f9a3e39b78a187809822e8bcf912f4c44a8" +
"92fe6a65a477ddea9582738317317286a2610ba30b6b090c3b8c61ffb64207229b3f01afe928a960" +
"c5a44c24b26f5f91";
BigInteger keyInt = new BigInteger(publicModulus, 16);
BigInteger exponentInt = new BigInteger("10001", 16);
RSAPublicKeySpec keySpeck = new RSAPublicKeySpec(keyInt, exponentInt);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
publicKey = keyFactory.generatePublic(keySpeck);
}
private void createPrivateKey() throws NoSuchAlgorithmException, InvalidKeySpecException {
String privateModulus = "6c97ab6369cf00dd174bacd7c37e6f661d04e5af10670d4d88d30148ec188e63227b8dac0c517cf9" +
"67aa73cd23684c9165dc269f091bfab33b6c5c7db95b54130e348255c30aaaac1c7f09ef701e0d6f" +
"6dc142d2e4ed78466cc104e28d50be7adf3863afc021dbdd8b5f0b968b7cd965242c7d8d4b32ee84" +
"0fac3cad134344c1";
BigInteger privateModulusInt = new BigInteger(privateModulus, 16);
BigInteger exponentInt = new BigInteger("10001", 16);
RSAPrivateKeySpec privateKeySpec = new RSAPrivateKeySpec(privateModulusInt, exponentInt);
KeyFactory factory = KeyFactory.getInstance("RSA");
privateKey = factory.generatePrivate(privateKeySpec);
}
在主要方法中，我有以下内容：
createPrivateKey();
createPublicKey();
String data = "12";
Cipher cipher1 = Cipher.getInstance("RSA/ECB/NoPadding");
cipher1.init(Cipher.ENCRYPT_MODE, publicKey);
byte[] encryptedData = cipher1.doFinal(data.getBytes());
Cipher cipher2 = Cipher.getInstance("RSA/ECB/NoPadding");
cipher2.init(Cipher.DECRYPT_MODE,privateKey);
byte[] decryptedData = cipher2.doFinal(encryptedData);
System.out.println(new String(decryptedData));
在控制台中我得到以下内容： .7 p;％kV 9y xa ɼ{而不是"12"如果我制作String data = "12345";，我然后得到：javax.crypto.BadPaddingException: Message is larger than modulus
首先为什么加密和解密不起作用？为什么我没有回来"12"。其次，为什么我的数据不能大于2个字符？
注意我正在使用以下website来获取模数和指数值。
答案 0 :(得分：2)
创建私钥时出错。你提供公共指数而不是私人和（如评论@ dave_thomsom_085）私人指数而不是模数
使用
更改.smt
createPrivateKey()出于安全原因，您也不应在没有填充的情况下使用原始RSA。使用private static PrivateKey createPrivateKey() throws NoSuchAlgorithmException, InvalidKeySpecException {
String publicModulus = "d2c34017ef94f8ab6696dae66e3c0d1ad186bbd9ce4461b68d7cd017c15bda174045bfef36fbf048" +
"73cfd6d09e3806af3949f99c3e09d6d3c37f6398d8c63f9a3e39b78a187809822e8bcf912f4c44a8" +
"92fe6a65a477ddea9582738317317286a2610ba30b6b090c3b8c61ffb64207229b3f01afe928a960" +
"c5a44c24b26f5f91";
String privateExponent = "6c97ab6369cf00dd174bacd7c37e6f661d04e5af10670d4d88d30148ec188e63227b8dac0c517cf9" +
"67aa73cd23684c9165dc269f091bfab33b6c5c7db95b54130e348255c30aaaac1c7f09ef701e0d6f" +
"6dc142d2e4ed78466cc104e28d50be7adf3863afc021dbdd8b5f0b968b7cd965242c7d8d4b32ee84" +
"0fac3cad134344c1";
BigInteger privateExponenInt = new BigInteger(privateExponent, 16);
BigInteger keyInt = new BigInteger(publicModulus, 16);
RSAPrivateKeySpec privateKeySpec = new RSAPrivateKeySpec(keyInt, privateExponenInt);
KeyFactory factory = KeyFactory.getInstance("RSA");
return factory.generatePrivate(privateKeySpec);
}
或新的OAEP填充RSA/ECB/PKCS1Padding
根据this answer，您可以使用RSA/ECB/OAEPWithSHA1AndMGF1Padding数据加密，最多比密钥大小少11个字节。 and using OAEP它必须小于键模数的大小 - 41
然后，使用您的1024位密钥：
PKCS1Padding (1024 bits / 8) - 11 = 117 bytes 还建议直接使用CRT代替私有指数
(1024 bits / 8) - 42 = 86 bytes