120 lines
5.1 KiB
Java
120 lines
5.1 KiB
Java
package org.moparscape.msc.gs.util;
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/*************************************************************************
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* Compilation: javac RSA.java
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* Execution: java RSA N
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*
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* Generate an N-bit public and private RSA key and use to encrypt
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* and decrypt a random message.
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*
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* % java RSA 50
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* public = 65537
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* private = 553699199426609
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* modulus = 825641896390631
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* message = 48194775244950
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* encrpyted = 321340212160104
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* decrypted = 48194775244950
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*
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* Known bugs (not addressed for simplicity)
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* -----------------------------------------
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* - It could be the case that the message >= modulus. To avoid, use
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* a do-while loop to generate key until modulus happen to be exactly N bits.
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*
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* - It's possible that gcd(phi, publicKey) != 1 in which case
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* the key generation fails. This will only happen if phi is a
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* multiple of 65537. To avoid, use a do-while loop to generate
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* keys until the gcd is 1.
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*
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*************************************************************************/
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import java.math.BigInteger;
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import java.security.KeyFactory;
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import java.security.KeyPair;
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import java.security.KeyPairGenerator;
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import java.security.NoSuchAlgorithmException;
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import java.security.PrivateKey;
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import java.security.PublicKey;
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import java.security.spec.PKCS8EncodedKeySpec;
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import java.security.spec.X509EncodedKeySpec;
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import javax.crypto.Cipher;
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public class RSA {
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private static KeyFactory keyFactory;
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private static PublicKey pubKey;
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private static PrivateKey privKey;
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static {
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try {
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keyFactory = KeyFactory.getInstance("RSA");
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pubKey = keyFactory
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.generatePublic(new X509EncodedKeySpec(
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new BigInteger(
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"258483531987721813854435365666199783121097212864526576114955744050873252978581213214062885665119329089273296913884093898593877564098511382732309048889240854054459372263273672334107564088395710980478911359605768175143527864461996266529749955416370971506195317045377519645018157466830930794446490944537605962330090699836840861268493872513762630835769942133970804813091619416385064187784658945")
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.toByteArray()));
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privKey = keyFactory
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.generatePrivate(new PKCS8EncodedKeySpec(
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new BigInteger(
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"126389230230897930352385109045517175528919326976939639978192012327670621489047580094424093866394604083620710942258641479882605306217705080633073206358002116577711775977035174649355992840385149147227804978220431329886904749249047207172981994234190017310148273188617548379533657419013879671232142718169518429371391936849151606245205570182197305333898616362563500262673852314745836689909720746451418490347388427381974609081779036643692442896601636017446393710362921966444628494554137329105609231821252714960402427087902143625637826354987050179190296311361184976459578647089802255916487029562372894817902016349527418080110572755696829671001527629662007011502494795321796989748708894483748787746164007093796775322700601606206239680220934740393355136437625692864876018489463040975412867784876767858234777778613227623572162881295529316433265197827292214481807179049611685053128209907494051691218003161010138655935539925662842276881932027193524730598562717449099166747466602094321757382874332291191770626601705016723177033286335759178872988144726412991304849553921854275796353460611722080118921976660955130059428940619614317969278356912087565839497213220194655672243883744862866647835331423918525974671607339058850826043973690788036967549648769172496014048685165109400959786151179359607410101378890865847238149636112094448917842512853709764865360978231071734030322981843223939320472985117985802975969976688950242865772248639234517663026594659960052526081995926396802458422109485608674299402862528020107837865224663685601410678473927829")
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.toByteArray()));
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} catch (Exception e) {
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}
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}
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/**
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* Decrypt text using private key
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*
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* @param text
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* The encrypted text
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* @param key
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* The private key
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* @return The unencrypted text
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* @throws java.lang.Exception
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*/
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public static byte[] decrypt(byte[] text) throws Exception {
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byte[] dectyptedText = null;
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Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
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cipher.init(Cipher.DECRYPT_MODE, privKey);
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dectyptedText = cipher.doFinal(text);
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return dectyptedText;
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}
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/**
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* Encrypt a text using public key.
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*
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* @param text
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* The original unencrypted text
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* @param key
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* The public key
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* @return Encrypted text
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* @throws java.lang.Exception
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*/
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public static byte[] encrypt(byte[] text) throws Exception {
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byte[] cipherText = null;
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Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
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cipher.init(Cipher.ENCRYPT_MODE, pubKey);
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cipherText = cipher.doFinal(text);
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return cipherText;
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}
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/**
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* Generate key which contains a pair of privae and public key using 1024
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* bytes
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*
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* @return key pair
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* @throws NoSuchAlgorithmException
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*/
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public static KeyPair generateKey() throws NoSuchAlgorithmException {
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KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
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keyGen.initialize(1024);
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KeyPair key = keyGen.generateKeyPair();
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return key;
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}
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}
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