这让我很难过 – 以下代码使用SpongyCastle的Android加密/解密 – 我正在尝试为iOS实现跨平台加密/解密.

下面的代码(来自Android)使用PKCS7Padding处理AES 128bit CBC,使用提供的salt和密码,salt存储在MysqL数据库中,密码由最终用户提供,以下代码改编自此回答kelhoer.

我之所以使用AES128bit是因为AES256在iOS 4中不可用,它是在iOS5中引入的,并且不得不使用openssl来生成派生密钥和初始化向量(iv),因为学到苹果拒绝它是很冒险的与openssl库静态链接的应用程序.

由于该平台基于iOS 4.2,使用bundling and statically linking the openssl库似乎相当,过度杀死并且最好使用CommonCryptor库.

这是使用Spongycastle代码的Android版本：

private static void encrypt(InputStream fin,OutputStream fout,String password,byte[] bSalt) {
    try {
        PKCS12ParametersGenerator pGen = new PKCS12ParametersGenerator(
            new SHA256Digest()
            );
        char[] passwordChars = password.tocharArray();
        final byte[] pkcs12PasswordBytes = 
            PBEParametersGenerator.PKCS12PasswordToBytes(passwordChars);
        pGen.init(pkcs12PasswordBytes,bSalt,ITERATIONS);
        CBCBlockCipher aesCBC = new CBCBlockCipher(new AESEngine());
        ParametersWithIV aesCBCParams = 
            (ParametersWithIV) pGen.generateDerivedParameters(128,128);
        aesCBC.init(true,aesCBCParams);
        PaddedBufferedBlockCipher aesCipher = 
            new PaddedBufferedBlockCipher(aesCBC,new PKCS7Padding());
        aesCipher.init(true,aesCBCParams);
        byte[] buf = new byte[BUF_SIZE];
        // Read in the decrypted bytes and write the cleartext to out
        int numRead = 0;
        while ((numRead = fin.read(buf)) >= 0) {
            if (numRead == 1024) {
                byte[] plainTemp = new byte[
                    aesCipher.getUpdateOutputSize(numRead)];
                int offset = 
                    aesCipher.processBytes(buf,numRead,plainTemp,0);
                final byte[] plain = new byte[offset];
                System.arraycopy(plainTemp,plain,plain.length);
                fout.write(plain,plain.length);
            } else {
                byte[] plainTemp = new byte[aesCipher.getOutputSize(numRead)];
                int offset = 
                    aesCipher.processBytes(buf,0);
                int last = aesCipher.doFinal(plainTemp,offset);
                final byte[] plain = new byte[offset + last];
                System.arraycopy(plainTemp,plain.length);
            }
        }
        fout.close();
        fin.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

}

private static void decrypt(InputStream fin,128);
        aesCBC.init(false,new PKCS7Padding());
        aesCipher.init(false,0);
                // int last = aesCipher.doFinal(plainTemp,offset);
                final byte[] plain = new byte[offset];
                System.arraycopy(plainTemp,plain.length);
            } else {
                byte[] plainTemp = new byte[
                    aesCipher.getOutputSize(numRead)];
                int offset = 
                    aesCipher.processBytes(buf,plain.length);
            }
        }
        fout.close();
        fin.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

但是在iOS 4.2(使用XCode)下我无法弄清楚如何做等效的,

这就是我在Objective C下尝试过的,其目标是解密来自Android端的数据,存储在MysqL数据库中,以测试它：

+(NSData*) decrypt:(NSData*)cipherData 
    userPassword:(NSString*)argPassword 
    genSalt:(NSData*)argPtrSalt{

    size_t szPlainBufLen = cipherData.length + (kCCBlockSizeAES128);
    uint8_t *ptrPlainBuf = malloc(szPlainBufLen);
    //
    const unsigned char *ptrPasswd = 
        (const unsigned char*)[argPassword 
            cStringUsingEncoding:NSASCIIStringEncoding];
    int ptrPasswdLen = strlen(ptrPasswd);
    //
    NSString *ptrSaltStr = [[NSString alloc]
        initWithData:argPtrSalt 
        encoding:NSASCIIStringEncoding];

    const unsigned char *ptrSalt = 
        (const unsigned char *)[ptrSaltStr UTF8String];
    NSString *ptrCipherStr = 
        [[NSString alloc]initWithData:cipherData 
            encoding:NSASCIIStringEncoding];
    unsigned char *ptrCipher = (unsigned char *)[ptrCipherStr UTF8String];
    unsigned char key[kCCKeySizeAES128];
    unsigned char iv[kCCKeySizeAES128];
    //
    //int     EVP_BytesToKey(const EVP_CIPHER *type,const EVP_MD *md,//const unsigned char *salt,const unsigned char *data,//int datal,int count,unsigned char *key,unsigned char *iv);
    int i = EVP_BytesToKey(EVP_aes_128_cbc(),EVP_sha256(),ptrSalt,ptrPasswd,ptrPasswdLen,PBKDF2_ITERATIONS,key,iv);
    NSAssert(i == kCCKeySizeAES128,@"Unable to generate key for AES");
    //
    size_t cipherLen = [cipherData length];
    size_t outlength = 0;
    //
    CCCryptorStatus resultCCStatus = CCCrypt(kCCDecrypt,kCCAlgorithmAES128,kCCOptionPKCS7Padding,kCCBlockSizeAES128,iv,ptrCipher,cipherLen,ptrPlainBuf,szPlainBufLen,&outlength);
    NSAssert(resultCCStatus == kCCSuccess,@"Unable to perform PBE AES128bit decryption: %d",errno);
    NSData *ns_dta_PlainData = nil;

    if (resultCCStatus == kCCSuccess){
        ns_dta_PlainData = 
        [NSData dataWithBytesNoCopy:ptrPlainBuf length:outlength];
    }else{
        return nil;
    }
    return ns_dta_PlainData;
}

提供了数据和用户密码,并从CCCrypt获得返回码为-4304,表示解码不成功和错误.

我原以为编码方案可能会抛弃CommonCryptor的解密路由,因此转换为NSASCIIStringEncoding的方法很冗长.

Salt与密码数据一起存储,长度为32字节.

考虑到密码学方面的问题,我在这方面缺少什么.