Question

我对密码学有点新意，需要我

“创建或检索用户的RSA-OAEP密钥。应该有一个设备“
的每个用户的公钥/私钥对

并以此格式将其发送到服务器：

{"modulus":"qMBRpdYrAy5aMmo31NErUizh5sbweguSmh4wlK6uJEIDl+kwTlROnE34KOFExeTbJSX0WygPi+vWl0yNq7buIMUKpytossAAWut5khO3CQJxTk7G2gnEPNUUXHiExGgNrLzcSLv8YIlfVALhoRWyC67KOL+a+3taNq3h+BHeWhM=","exponent":"AQAB"}

我尝试使用OpenSSL命令生成RSA公钥/私钥对，它出现如下：

公钥（为了安全起见，已将值更改了一点）：

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC4NMwqhswK6Py+N1OlPBn3JelqEdZ8YwSn4j1Kvp5HK+pS/5gcABkx/89buDhhtKvZ8mfSNkhKHU2WuBPIikGAvEKbbbQ8DHKubHa07X1xTgY+qMyxTLaHnaEC6oOi6BixPfo6QAm+SnqxBWuvDPBzGqSS+/p5r7aydLBAlkoZ+DzpBbAHIIK72c+xqCL8oOFz4QqsVMakdKQ+fVdM1e8U2ak4ygHOleqJgcl8+xH7TFJsvUOfsgsMlz2FmNXWhCYUdOKglP8ZUVMuiAW9KEjAFta4xEf3bBGRDYss7mLQF5/RHbpzYeNwQ1RVp8bhTumpQytqJZshUj8DA3oqMFUr xyz@xyz.xyz

私钥（为了安全起见，已将值改变一点）：

如何从服务器期望的数据中提取模数和指数？

Answer 1

您只需从RFC 4253获取格式，但您需要找出来自RFC 4251的mpint（多精度整数）格式。

这是Java中的东西（只是 Java），只是因为JSch库非常糟糕。

package nl.owlstead.crypto;

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPublicKeySpec;
import java.util.Arrays;
import java.util.Base64;
import java.util.Base64.Encoder;

public class SSHPublicKeyDecoder {

    private static byte[] SSH_RSA_HEADER = "ssh-rsa".getBytes(StandardCharsets.US_ASCII);

    private static RSAPublicKey decodeRSAPublicKey(byte[] encodedRSAPublicKey)
            throws NoSuchAlgorithmException, InvalidKeySpecException {
        ByteBuffer buf = ByteBuffer.wrap(encodedRSAPublicKey);

        byte[] header = getSSHEncodedValueFromBuffer(buf);
        if (!Arrays.equals(header, SSH_RSA_HEADER)) {
            throw new IllegalArgumentException("Not an RSA public key");
        }

        byte[] eDataSigned = getSSHEncodedValueFromBuffer(buf);
        BigInteger e = new BigInteger(eDataSigned);

        byte[] nDataSigned = getSSHEncodedValueFromBuffer(buf);
        BigInteger n = new BigInteger(nDataSigned);

        KeyFactory rsaKeyFactory;
        try {
            rsaKeyFactory = KeyFactory.getInstance("RSA");
        } catch (NoSuchAlgorithmException ex) {
            throw new IllegalStateException(
                    "KeyFactory should exist for RSA", ex);
        }

        RSAPublicKeySpec spec = new RSAPublicKeySpec(n, e);
        return (RSAPublicKey) rsaKeyFactory.generatePublic(spec);
    }

    private static byte[] getSSHEncodedValueFromBuffer(ByteBuffer buf) {
        int size = buf.getInt();
        if (size < 0) {
            throw new IllegalArgumentException("Bad SSH encoded value in format");
        }
        byte[] data = new byte[size];
        buf.get(data);
        return data;
    }

    private static byte[] toUnsigned(BigInteger value) {
        if (value.compareTo(BigInteger.ZERO) <= 0) {
            throw new IllegalArgumentException("Negative numbers cannot be encoded as unsigned integers");
        }

        if (value.equals(BigInteger.ZERO)) {
            return value.toByteArray();
        }

        final byte[] signedBigEndian = value.toByteArray();

        if (signedBigEndian[0] == 0x00) {
            return Arrays.copyOfRange(signedBigEndian, 1, signedBigEndian.length);
        }

        return signedBigEndian;
    }

    private SSHPublicKeyDecoder() {

    }

    public static void main(String[] args) throws Exception {
        String[] parts = args[0].split("\\s+");
        String part2 = parts[1];
        byte[] encodedRSAPublicKey = Base64.getDecoder().decode(part2);

        RSAPublicKey pubKey = decodeRSAPublicKey(encodedRSAPublicKey);
        String format = encodeServerPublicKey(pubKey);

        System.out.println(format);
    }

    private static String encodeServerPublicKey(RSAPublicKey pubKey) {
        byte[] nData = toUnsigned(pubKey.getModulus());
        byte[] eData = toUnsigned(pubKey.getPublicExponent());

        Encoder base64Encoder = Base64.getEncoder();
        String format = String.format(
                "{\"modulus\":\"%s\",\"exponent\":\"%s\"}%n",
                base64Encoder.encodeToString(nData),
                base64Encoder.encodeToString(eData));
        return format;
    }
}

如何获取RSA公钥和私钥并以纯文本形式获得模数和指数？

1 个答案: