关于iOS aes256加密的问题，请各位帮忙，搞了一个星期，急求答案！

鉴于rsa加密的重要性和相关源代码的匮乏 经过整理特此贴出 需要下载bcprov jdk jar import javax crypto Cipher;import java security ;import java security spec RSAPublicKeySpec;import java security spec RSAPrivateKeySpec;import java security spec InvalidKeySpecException;import java security interfaces RSAPrivateKey;import java security interfaces RSAPublicKey;import java io ;import java math BigInteger;/ RSA 工具类 提供加密 解密 生成密钥对等方法 需要到下载bcprov jdk jar /public class RSAUtil {/ 生成密钥对 @return KeyPair @throws EncryptException/public static KeyPair generateKeyPair() throws EncryptException {try {KeyPairGenerator keyPairGen = KeyPairGenerator getInstance( RSA new bouncycastle jce provider BouncyCastleProvider());final int KEY_SIZE = ;//没什么好说的了 这个值关系到块加密的大小 可以更改 但是不要太大 否则效率会低keyPairGen initialize(KEY_SIZE new SecureRandom());KeyPair keyPair = keyPairGen genKeyPair();return keyPair;} catch (Exception e) {throw new EncryptException(e getMessage());}}/ 生成公钥 @param modulus @param publicExponent @return RSAPublicKey @throws EncryptException/public static RSAPublicKey generateRSAPublicKey(byte[] modulus byte[] publicExponent) throws EncryptException {KeyFactory keyFac = null;try {keyFac = KeyFactory getInstance( RSA new bouncycastle jce provider BouncyCastleProvider());} catch (NoSuchAlgorithmException ex) {throw new EncryptException(ex getMessage());}RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus) new BigInteger(publicExponent));try {return (RSAPublicKey) keyFac generatePublic(pubKeySpec);} catch (InvalidKeySpecException ex) {throw new EncryptException(ex getMessage());}}/ 生成私钥 @param modulus @param privateExponent @return RSAPrivateKey @throws EncryptException/public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus byte[] privateExponent) throws EncryptException {KeyFactory keyFac = null;try {keyFac = KeyFactory getInstance( RSA new bouncycastle jce provider BouncyCastleProvider());} catch (NoSuchAlgorithmException ex) {throw new EncryptException(ex getMessage());}RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus) new BigInteger(privateExponent));try {return (RSAPrivateKey) keyFac generatePrivate(priKeySpec);} catch (InvalidKeySpecException ex) {throw new EncryptException(ex getMessage());}}/ 加密 @param key 加密的密钥 @param data 待加密的明文数据 @return 加密后的数据 @throws EncryptException/public static byte[] encrypt(Key key byte[] data) throws EncryptException {try {Cipher cipher = Cipher getInstance( RSA new bouncycastle jce provider BouncyCastleProvider());cipher init(Cipher ENCRYPT_MODE key);int blockSize = cipher getBlockSize();//获得加密块大小 如 加密前数据为 个byte 而key_size= 加密块大小为 byte 加密后为 个byte;因此共有 个加密块 第一个 byte第二个为 个byteint outputSize = cipher getOutputSize(data length);//获得加密块加密后块大小int leavedSize = data length % blockSize;int blocksSize = leavedSize != data length / blockSize + : data length / blockSize;byte[] raw = new byte[outputSize blocksSize];int i = ;while (data length i blockSize > ) {if (data length i blockSize > blockSize)cipher doFinal(data i blockSize blockSize raw i outputSize);elsecipher doFinal(data i blockSize data length i blockSize raw i outputSize);//这里面doUpdate方法不可用 查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到ByteArrayOutputStream中 而最后doFinal的时候才将所有的byte[]进行加密 可是到了此时加密块大小很可能已经超出了OutputSize所以只好用dofinal方法 i++;}return raw;} catch (Exception e) {throw new EncryptException(e getMessage());}}/ 解密 @param key 解密的密钥 @param raw 已经加密的数据 @return 解密后的明文 @throws EncryptException/public static byte[] decrypt(Key key byte[] raw) throws EncryptException {try {Cipher cipher = Cipher getInstance( RSA new bouncycastle jce provider BouncyCastleProvider());cipher init(cipher DECRYPT_MODE key);int blockSize = cipher getBlockSize();ByteArrayOutputStream bout = new ByteArrayOutputStream( );int j = ;while (raw length j blockSize > ) {bout write(cipher doFinal(raw j blockSize blockSize));j++;}return bout toByteArray();} catch (Exception e) {throw new EncryptException(e getMessage());}}/ @param args @throws Exception/public static void main(String[] args) throws Exception {File file = new File( l );FileInputStream in = new FileInputStream(file);ByteArrayOutputStream bout = new ByteArrayOutputStream();byte[] tmpbuf = new byte[ ];int count = ;while ((count = in read(tmpbuf)) != ) {bout write(tmpbuf count);tmpbuf = new byte[ ];}in close();byte[] Data = bout toByteArray();KeyPair keyPair = RSAUtil generateKeyPair();RSAPublicKey pubKey = (RSAPublicKey) keyPair getPublic();RSAPrivateKey priKey = (RSAPrivateKey) keyPair getPrivate();byte[] pubModBytes = pubKey getModulus() toByteArray();byte[] pubPubExpBytes = pubKey getPublicExponent() toByteArray();byte[] priModBytes = priKey getModulus() toByteArray();byte[] priPriExpBytes = priKey getPrivateExponent() toByteArray();RSAPublicKey recoveryPubKey = RSAUtil generateRSAPublicKey(pubModBytes pubPubExpBytes);RSAPrivateKey recoveryPriKey = RSAUtil generateRSAPrivateKey(priModBytes priPriExpBytes);byte[] raw = RSAUtil encrypt(priKey Data);file = new File( encrypt_result dat );OutputStream out = new FileOutputStream(file);out write(raw);out close();byte[] data = RSAUtil decrypt(recoveryPubKey raw);file = new File( l );out = new FileOutputStream(file);out write(data);out flush();out close();}}加密可以用公钥 解密用私钥 或者加密用私钥 通常非对称加密是非常消耗资源的 因此可以对大数据用对称加密如 des（具体代码可以看我以前发的贴子） 而对其对称密钥进行非对称加密 这样既保证了数据的安全 还能保证效率 lishixinzhi/Article/program/Java/gj/201311/27391

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