From 566d17f731637df6828bdf32502a0fb123882dbe Mon Sep 17 00:00:00 2001
From: Peter Palfrader <peter@palfrader.org>
Date: Thu, 9 Oct 2003 11:41:45 +0000
Subject: Initial import

---
 .../noreply/fancydress/crypto/RSAPublicKey.java    | 125 +++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 src/org/noreply/fancydress/crypto/RSAPublicKey.java

(limited to 'src/org/noreply/fancydress/crypto/RSAPublicKey.java')

diff --git a/src/org/noreply/fancydress/crypto/RSAPublicKey.java b/src/org/noreply/fancydress/crypto/RSAPublicKey.java
new file mode 100644
index 0000000..13f8b53
--- /dev/null
+++ b/src/org/noreply/fancydress/crypto/RSAPublicKey.java
@@ -0,0 +1,125 @@
+package org.noreply.fancydress.crypto;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.UnsupportedEncodingException;
+import org.bouncycastle.asn1.DEROctetString;
+import org.bouncycastle.asn1.ASN1Sequence;
+import org.bouncycastle.asn1.DERInputStream;
+import org.bouncycastle.asn1.x509.RSAPublicKeyStructure;
+import org.bouncycastle.crypto.AsymmetricBlockCipher;
+import org.bouncycastle.crypto.InvalidCipherTextException;
+import org.bouncycastle.crypto.engines.RSAEngine;
+import org.bouncycastle.crypto.digests.SHA1Digest;
+import org.bouncycastle.crypto.encodings.OAEPEncoding;
+import org.bouncycastle.crypto.params.RSAKeyParameters;
+import org.noreply.fancydress.misc.Util;
+
+/**
+ * This class is a wrapper for the bouncycastle RSA functionality.
+ */
+public class RSAPublicKey {
+	/**
+	 * The overhead (in octets) added by OAEP padding.
+	 */
+	public static final int PK_OVERHEAD_LEN = 42;
+	/**
+	 * The length of encrypted data. (we use 2048 bit keys)
+	 */
+	public static final int PK_ENC_LEN = 256;
+	/**
+	 * The maximum amount of octets that can be encoded in an RSA message.
+	 */
+	public static final int PK_MAX_DATA_LEN = PK_ENC_LEN - PK_OVERHEAD_LEN;
+
+	/**
+	 * the RSA cipher from bouncycastle.
+	 */
+	private AsymmetricBlockCipher rsa_cipher;
+	/**
+	 * a key structure
+	 */
+	private RSAPublicKeyStructure key;
+	/**
+	 * key parameters
+	 */
+	private RSAKeyParameters keyParams;
+
+	/**
+	 * Construct an instance of an RSAPublicKey from the ASN1 encoded key.
+	 *
+	 * @param asnEncoded ASN1 encoded RSA key.
+	 */
+	public RSAPublicKey(byte[] asnEncoded) {
+		String p   = new String("He who would make his own liberty secure, must guard even his enemy from oppression.");
+		rsa_cipher = new OAEPEncoding(new RSAEngine(), new SHA1Digest(), CryptoPrimitives.hash(Util.toOctets(p)));
+
+		ByteArrayInputStream     bIn = new ByteArrayInputStream(asnEncoded);
+		DERInputStream           dIn = new DERInputStream(bIn);
+		try {
+			key                  = new RSAPublicKeyStructure((ASN1Sequence)dIn.readObject());
+		} catch (IOException e) {
+			throw new Error(e);
+		}
+		keyParams                    = new RSAKeyParameters(false, key.getModulus(), key.getPublicExponent());
+	};
+	/**
+	 * Encrypt a message.
+	 *
+	 * Encrypts message m to this key.
+	 * 
+	 * @param m the message to encrypt.
+	 * @return the encrypted message (PK_ENC_LEN octets long)
+	 */
+	public byte[] encrypt(byte[] m) {
+		rsa_cipher.init(true, keyParams);
+		byte[] result;
+		try {
+			result = rsa_cipher.processBlock(m, 0, m.length);
+		} catch (InvalidCipherTextException e) {
+			throw new Error(e);
+		}
+		return(result);
+	}
+	/**
+	 * Verify a signature.
+	 *
+	 * Verify that the information signed in signature <code>sig</code>
+	 * matches the value in <code>m</code>.
+	 *
+	 * @param sig the signature
+	 * @param m message to compare the signed information to
+	 * @return true if the signature is valid
+	 * @throws InvalidCipherTextException
+	 */
+	public boolean verify(byte[] sig, byte[] m) throws InvalidCipherTextException {
+		rsa_cipher.init(false, keyParams);
+		byte[] signedDigest = rsa_cipher.processBlock(sig, 0, sig.length);
+		byte[] digest = CryptoPrimitives.hash(m);
+		boolean verifies = Util.equal(digest, signedDigest);
+		return(verifies);
+	}
+	/**
+	 * Return the ASN 1 encoding of this key.
+	 *
+	 * @return this key, asn1 encoded
+	 */
+	public byte[] encode() {
+		DEROctetString asn = new DEROctetString(key);
+		byte[] result = asn.getOctets();
+		return(result);
+	}
+	/**
+	 * Get this key's fingerprint.
+	 *
+	 * The fingerprint (or keyid) is the hash of the asn1 representation of this key.
+	 *
+	 * @return the fingerprint.
+	 */
+	public byte[] getFingerprint() {
+		DEROctetString asn = new DEROctetString(key);
+		byte[] encoded = asn.getOctets();
+		byte[] result = CryptoPrimitives.hash(encoded);
+		return(result);
+	}
+}
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