错误：RSA密钥长度必须至少为512位？ [英] Error: RSA Keys must be at least 512 bits long?

问题描述

我正在尝试使用一个使用模数和指数来生成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 - < ---的行是错误发生的地方。

I'm attempting to make an application that uses a modulus and exponent to generate a public key for RSA. However, there is the issue that the modulus and exponent are both possibly hex values. This is the code that I have for generating the key, the line marked with the -<--- is where the error is occuring.

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;
}

将放在这里的示例模数和指数如下： / p>

An example modulus and exponent that would be put into this are as follows:

modulus:"B31F9097CA38B4548D7300A0768F262C58D92B190355E382DACA4B79DA52226758FD8EB23CE29F404433411AC90308BEEED093BA157E03982E587496A15BB47A371C32C6B665FF75D6E900CF28CF679E871FB06FF0E90431E829DBE8EBDF7D5024A2D32F8B0D50C0D592E5D31046DE275F81B106088EBECA434493458DBF2B804BC46EC973E8F47408CC454F03F24933A5B100001B47239B44A52CF6A40670CED35060EB84BD6D0829DF8EC84EC49D784CA8583F353086071604DB2F43FA243A05F031033FFB179D8CB281A814B01F8CCC2EC29196BB136905104E23832FA923185743E18924C4E9772ED094D98643C677DE99EF1E598452728A7AC3DF5A1AB9"

exponent：010001

堆栈跟踪大部分是： / p>

The stack trace, for the most part:

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，因为我的RSA加密知识有限。如果有人可以帮我弄清楚为什么这个错误不断出现，这将是非常有用的：）

I'm not going to pretend that I know why this error is happening because my knowledge with RSA encryption is somewhat limited. If anyone could help me figure out why this error keeps cropping up, it would be extremely helpful :)

推荐答案

根据 http://docs.oracle.com/javase/ 7 / docs / api / java / security / spec / RSAPublicKeySpec.html 将参数交换到 RSAPublicKeySpec 构造函数：模数首先是指数秒。

According to http://docs.oracle.com/javase/7/docs/api/java/security/spec/RSAPublicKeySpec.html you swapped the arguments to the RSAPublicKeySpec constructor: The modulus goes first, the exponent second.

此外，不要自己实现Hex - > BigInteger 转换。使用新的BigInteger（hexString，16）（请参阅这个答案）

Also, don't implement the Hex -> BigInteger conversion yourself. Use new BigInteger( hexString, 16 ) (See this answer)

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