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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8. Note: this package includes the NTRU encryption algorithms.

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package org.bouncycastle.crypto.util;

import java.io.IOException;
import java.math.BigInteger;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.params.DSAParameters;
import org.bouncycastle.crypto.params.DSAPublicKeyParameters;
import org.bouncycastle.crypto.params.ECNamedDomainParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.params.Ed25519PublicKeyParameters;
import org.bouncycastle.crypto.params.RSAKeyParameters;
import org.bouncycastle.math.ec.ECCurve;


/**
 * OpenSSHPublicKeyUtil utility classes for parsing OpenSSH public keys.
 */
public class OpenSSHPublicKeyUtil
{
    private OpenSSHPublicKeyUtil()
    {

    }

    private static final String RSA = "ssh-rsa";
    private static final String ECDSA = "ecdsa";
    private static final String ED_25519 = "ssh-ed25519";
    private static final String DSS = "ssh-dss";

    /**
     * Parse a public key.
     * 

* This method accepts the bytes that are Base64 encoded in an OpenSSH public key file. * * @param encoded The key. * @return An AsymmetricKeyParameter instance. */ public static AsymmetricKeyParameter parsePublicKey(byte[] encoded) { SSHBuffer buffer = new SSHBuffer(encoded); return parsePublicKey(buffer); } /** * Encode a public key from an AsymmetricKeyParameter instance. * * @param cipherParameters The key to encode. * @return the key OpenSSH encoded. * @throws IOException */ public static byte[] encodePublicKey(AsymmetricKeyParameter cipherParameters) throws IOException { if (cipherParameters == null) { throw new IllegalArgumentException("cipherParameters was null."); } if (cipherParameters instanceof RSAKeyParameters) { if (cipherParameters.isPrivate()) { throw new IllegalArgumentException("RSAKeyParamaters was for encryption"); } RSAKeyParameters rsaPubKey = (RSAKeyParameters)cipherParameters; SSHBuilder builder = new SSHBuilder(); builder.writeString(RSA); builder.writeBigNum(rsaPubKey.getExponent()); builder.writeBigNum(rsaPubKey.getModulus()); return builder.getBytes(); } else if (cipherParameters instanceof ECPublicKeyParameters) { SSHBuilder builder = new SSHBuilder(); // // checked for named curve parameters.. // String name = SSHNamedCurves.getNameForParameters(((ECPublicKeyParameters)cipherParameters).getParameters()); if (name == null) { throw new IllegalArgumentException("unable to derive ssh curve name for " + ((ECPublicKeyParameters)cipherParameters).getParameters().getCurve().getClass().getName()); } builder.writeString(ECDSA + "-sha2-" + name); // Magic builder.writeString(name); builder.writeBlock(((ECPublicKeyParameters)cipherParameters).getQ().getEncoded(false)); //Uncompressed return builder.getBytes(); } else if (cipherParameters instanceof DSAPublicKeyParameters) { DSAPublicKeyParameters dsaPubKey = (DSAPublicKeyParameters)cipherParameters; DSAParameters dsaParams = dsaPubKey.getParameters(); SSHBuilder builder = new SSHBuilder(); builder.writeString(DSS); builder.writeBigNum(dsaParams.getP()); builder.writeBigNum(dsaParams.getQ()); builder.writeBigNum(dsaParams.getG()); builder.writeBigNum(dsaPubKey.getY()); return builder.getBytes(); } else if (cipherParameters instanceof Ed25519PublicKeyParameters) { SSHBuilder builder = new SSHBuilder(); builder.writeString(ED_25519); builder.writeBlock(((Ed25519PublicKeyParameters)cipherParameters).getEncoded()); return builder.getBytes(); } throw new IllegalArgumentException("unable to convert " + cipherParameters.getClass().getName() + " to private key"); } /** * Parse a public key from an SSHBuffer instance. * * @param buffer containing the SSH public key. * @return A CipherParameters instance. */ public static AsymmetricKeyParameter parsePublicKey(SSHBuffer buffer) { AsymmetricKeyParameter result = null; String magic = buffer.readString(); if (RSA.equals(magic)) { BigInteger e = buffer.readBigNumPositive(); BigInteger n = buffer.readBigNumPositive(); result = new RSAKeyParameters(false, n, e); } else if (DSS.equals(magic)) { BigInteger p = buffer.readBigNumPositive(); BigInteger q = buffer.readBigNumPositive(); BigInteger g = buffer.readBigNumPositive(); BigInteger pubKey = buffer.readBigNumPositive(); result = new DSAPublicKeyParameters(pubKey, new DSAParameters(p, q, g)); } else if (magic.startsWith(ECDSA)) { String curveName = buffer.readString(); ASN1ObjectIdentifier oid = SSHNamedCurves.getByName(curveName); X9ECParameters x9ECParameters = SSHNamedCurves.getParameters(oid); if (x9ECParameters == null) { throw new IllegalStateException("unable to find curve for " + magic + " using curve name " + curveName); } ECCurve curve = x9ECParameters.getCurve(); byte[] pointRaw = buffer.readBlock(); result = new ECPublicKeyParameters( curve.decodePoint(pointRaw), new ECNamedDomainParameters(oid, x9ECParameters)); } else if (ED_25519.equals(magic)) { byte[] pubKeyBytes = buffer.readBlock(); if (pubKeyBytes.length != Ed25519PublicKeyParameters.KEY_SIZE) { throw new IllegalStateException("public key value of wrong length"); } result = new Ed25519PublicKeyParameters(pubKeyBytes, 0); } if (result == null) { throw new IllegalArgumentException("unable to parse key"); } if (buffer.hasRemaining()) { throw new IllegalArgumentException("decoded key has trailing data"); } return result; } }





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