Question

我正在尝试创建一个使用模数和指数生成RSA公钥的应用程序。但是，存在模数和指数都可能是十六进制值的问题。这是我生成密钥的代码，标有“＆lt; ---”的行是发生错误的地方。

RSAPublicKeySpec spec = new RSAPublicKeySpec(new BigInteger(1,hexToByte(rsaJSON.publickey_exp)),new BigInteger(1,hexToByte(rsaJSON.publickey_mod)));
KeyFactory factory = KeyFactory.getInstance("RSA");
PublicKey pub = factory.generatePublic(spec); <---
Cipher cipher = cipher = Cipher.getInstance("RSA/None/OAEPWithSHA1AndMGF1Padding", "BC");
cipher.init(Cipher.ENCRYPT_MODE, pub);
.....
String HEXES = "0123456789ABCDEF";
public static String byteToHex( byte [] raw ) {
    if ( raw == null ) {
      return null;
    }
    final StringBuilder hex = new StringBuilder( 2 * raw.length );
    for ( final byte b : raw ) {
      hex.append(HEXES.charAt((b & 0xF0) >> 4))
         .append(HEXES.charAt((b & 0x0F)));
    }
    return hex.toString();
}

public static byte[] hexToByte( String hexString){
    int len = hexString.length();
    byte[] ba = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
        ba[i/2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i+1), 16));
    }
    return ba;
}

将放入此示例的模数和指数如下：

modulus:"B31F9097CA38B4548D7300A0768F262C58D92B190355E382DACA4B79DA52226758FD8EB23CE29F404433411AC90308BEEED093BA157E03982E587496A15BB47A371C32C6B665FF75D6E900CF28CF679E871FB06FF0E90431E829DBE8EBDF7D5024A2D32F8B0D50C0D592E5D31046DE275F81B106088EBECA434493458DBF2B804BC46EC973E8F47408CC454F03F24933A5B100001B47239B44A52CF6A40670CED35060EB84BD6D0829DF8EC84EC49D784CA8583F353086071604DB2F43FA243A05F031033FFB179D8CB281A814B01F8CCC2EC29196BB136905104E23832FA923185743E18924C4E9772ED094D98643C677DE99EF1E598452728A7AC3DF5A1AB9"

exponent:"010001"

堆栈跟踪，大部分：

java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: RSA keys must be at least 512 bits long
at sun.security.rsa.RSAKeyFactory.engineGeneratePublic(Unknown Source)
at java.security.KeyFactory.generatePublic(Unknown Source)
    .....

我不会假装我知道为什么会发生这种错误，因为我对RSA加密的了解有限。如果有人能帮我弄清楚为什么这个错误不断出现，那将非常有帮助：）

Answer 1

根据http://docs.oracle.com/javase/7/docs/api/java/security/spec/RSAPublicKeySpec.html你将参数交换到RSAPublicKeySpec构造函数：模数先行，指数秒。

另外，不要实现Hex - ＆gt; BigInteger转换自己。使用new BigInteger( hexString, 16 )（请参阅this回答）

Answer 2

没有任何内容可以生成＆＃34;。

(modulus, exponent)元组是是公钥。

例如，我有一个Google的网络服务器的证书，如果我运行openssl x509 -in certfile.pem -text，这是输出的一部分：

    Subject Public Key Info:
        Public Key Algorithm: rsaEncryption
        RSA Public Key: (1024 bit)
            Modulus (1024 bit):
                00:a7:4b:85:b2:80:e5:94:03:6f:ca:4a:e5:6c:a9:
                71:80:a1:67:f7:b9:46:e8:26:b5:e9:bd:59:4f:7b:
                dd:1a:50:68:c7:3a:df:73:15:ce:a8:69:00:d4:27:
                09:a9:cd:e1:d1:6e:2d:c6:a3:e9:3b:d6:aa:94:63:
                83:1a:64:27:bf:fe:87:90:d4:e6:b8:e4:89:a8:76:
                23:15:13:e0:27:6b:38:0a:fa:1f:b1:ec:71:0a:ec:
                34:ff:0d:9c:1c:a7:d6:47:0f:ec:70:6c:2a:6b:89:
                90:f5:de:58:e9:4e:ae:4d:6f:f0:f1:ca:7d:72:c0:
                7a:79:94:28:fe:85:01:58:c9
            Exponent: 65537 (0x10001)

那就是它。 RSA公钥是模数和指数。我认为你有你需要的东西。

错误：RSA密钥长度必须至少为512位？

2 个答案: