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RSA,DES加解密

RSA,DES加解密

作者: 阿姣_0405 | 来源:发表于2018-09-26 15:48 被阅读0次

    RSA加密算法是一种非对称加密算法
    RSA算法是第一个能同时用于加密和数字签名的算法,也易于理解和操作

    DES全称为Data Encryption Standard,即数据加密标准,是一种使用密钥加密的块算法,1977年被美国联邦政府的国家标准局确定为联邦资料处理标准(FIPS),并授权在非密级政府通信中使用,随后该算法在国际上广泛流传开来。需要注意的是,在某些文献中,作为算法的DES称为数据加密算法(Data Encryption Algorithm,DEA),已与作为标准的DES区分开来。

    废话少说,贴代码,亲测可用
    .h文件的实现

    //
    //  Cryptor.h
    //
    //
    
    #import <Foundation/Foundation.h>
    
    @interface Cryptor : NSObject
    /*AES加密
     *key传16进制String类型
     */
    + (NSData *)AES128EncryptWithKeyStr:(NSString *)key iv:(NSString *)iv data:(NSData *)data;
    + (NSData *)AES128DecryptWithKeyStr:(NSString *)key iv:(NSString *)iv data:(NSData *)data;
    
    /*AES解密
     *key传NSData类型
     */
    + (NSData *)AES128EncryptWithKey:(NSData *)key iv:(NSData *)iv data:(NSData *)data;
    + (NSData *)AES128DecryptWithKey:(NSData *)key iv:(NSData *)iv data:(NSData *)data;
    
    
    /*RSA加密
     *传data和pubKey
     *return raw data
     */
    + (NSData *)RSAencryptData:(NSData *)data publicKey:(NSString *)pubKey;
    
    /*RSA加密
     *传data和privKey
     *return raw data
     */
    + (NSData *)RSAencryptData:(NSData *)data privateKey:(NSString *)privKey;
    
    /*RSA解密
     *传data和pubKey
     *return raw data
     */
    + (NSData *)RSAdecryptData:(NSData *)data publicKey:(NSString *)pubKey;
    
    /*RSA解密
     *传data和privKey
     *return raw data
     */
    + (NSData *)RSAdecryptData:(NSData *)data privateKey:(NSString *)privKey;
    
    + (NSString *)loadPubKeyWithPemName:(NSString *)pemName;
    
    /*
     *data转16进制字符串
     */
    + (NSString *)hexEncoding:(NSData*)data;
    
    /*
    *16进制转NSData
    */
    + (NSData *)hexDecoding:(NSString *)string;
    
    @end
    

    .m文件实现

    //
    //  Cryptor.m
    //
    
    #import "Cryptor.h"
    #import <CommonCrypto/CommonCryptor.h>
    #import "TVTools.h"
    
    @implementation Cryptor
    + (NSData *)AES128EncryptWithKeyStr:(NSString *)key iv:(NSString *)iv data:(NSData *)data {
        NSData *keyPtr = [Cryptor hexDecoding:key];
        NSData *ivPtr = [Cryptor hexDecoding:iv];
        NSUInteger dataLength = [data length];
        size_t bufferSize = dataLength + kCCBlockSizeAES128;
        void *buffer = malloc(bufferSize);
        size_t numBytesEncrypted = 0;
        CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                              kCCAlgorithmAES128,
                                              kCCOptionPKCS7Padding,
                                              keyPtr.bytes,
                                              kCCBlockSizeAES128,
                                              ivPtr.bytes,
                                              [data bytes],
                                              dataLength,
                                              buffer,
                                              bufferSize,
                                              &numBytesEncrypted);
        if (cryptStatus == kCCSuccess) {
            return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
        }
        free(buffer);
        return nil;
    }
    
    + (NSData *)AES128DecryptWithKeyStr:(NSString *)key iv:(NSString *)iv data:(NSData *)data {
        NSData *keyPtr = [Cryptor hexDecoding:key];
        NSData *ivPtr = [Cryptor hexDecoding:iv];
        NSUInteger dataLength = [data length];
        size_t bufferSize = dataLength + kCCBlockSizeAES128;
        void *buffer = malloc(bufferSize);
        size_t numBytesDecrypted = 0;
        CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                              kCCAlgorithmAES128,
                                              kCCOptionPKCS7Padding,
                                              keyPtr.bytes,
                                              kCCBlockSizeAES128,
                                              ivPtr.bytes,
                                              [data bytes],
                                              dataLength,
                                              buffer,
                                              bufferSize,
                                              &numBytesDecrypted);
        if (cryptStatus == kCCSuccess) {
            return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        }
        free(buffer);
        return nil;
    }
    
    + (NSData *)AES128EncryptWithKey:(NSData *)key iv:(NSData *)iv data:(NSData *)data {
        NSUInteger dataLength = [data length];
        size_t bufferSize = dataLength + kCCBlockSizeAES128;
        void *buffer = malloc(bufferSize);
        size_t numBytesEncrypted = 0;
        CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                              kCCAlgorithmAES128,
                                              kCCOptionPKCS7Padding,
                                              key.bytes,
                                              kCCBlockSizeAES128,
                                              iv.bytes,
                                              [data bytes],
                                              dataLength,
                                              buffer,
                                              bufferSize,
                                              &numBytesEncrypted);
        if (cryptStatus == kCCSuccess) {
            return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
        }
        free(buffer);
        return nil;
    }
    
    + (NSData *)AES128DecryptWithKey:(NSData *)key iv:(NSData *)iv data:(NSData *)data {
        NSUInteger dataLength = [data length];
        size_t bufferSize = dataLength + kCCBlockSizeAES128;
        void *buffer = malloc(bufferSize);
        size_t numBytesDecrypted = 0;
        CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                              kCCAlgorithmAES128,
                                              kCCOptionPKCS7Padding,
                                              key.bytes,
                                              kCCBlockSizeAES128,
                                              iv.bytes,
                                              [data bytes],
                                              dataLength,
                                              buffer,
                                              bufferSize,
                                              &numBytesDecrypted);
        if (cryptStatus == kCCSuccess) {
            return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        }
        free(buffer);
        return nil;
    }
    
    /*RSA加密
     *传data和pubKey
     *return raw data
     */
    + (NSData *)RSAencryptData:(NSData *)data publicKey:(NSString *)pubKey{
        if(!data || !pubKey){
            return nil;
        }
        SecKeyRef keyRef = [Cryptor addPublicKey:pubKey];
        if(!keyRef){
            return nil;
        }
        return [Cryptor encryptData:data withKeyRef:keyRef isSign:NO];
    }
    
    /*RSA加密
     *传data和privKey
     *return raw data
     */
    + (NSData *)RSAencryptData:(NSData *)data privateKey:(NSString *)privKey{
        if(!data || !privKey){
            return nil;
        }
        SecKeyRef keyRef = [Cryptor addPrivateKey:privKey];
        if(!keyRef){
            return nil;
        }
        return [Cryptor encryptData:data withKeyRef:keyRef isSign:YES];
    }
    
    /*RSA解密
     *传data和pubKey
     *return raw data
     */
    + (NSData *)RSAdecryptData:(NSData *)data publicKey:(NSString *)pubKey{
        if(!data || !pubKey){
            return nil;
        }
        SecKeyRef keyRef = [Cryptor addPublicKey:pubKey];
        if(!keyRef){
            return nil;
        }
        return [Cryptor decryptData:data withKeyRef:keyRef];
    }
    
    /*RSA解密
     *传data和privKey
     *return raw data
     */
    + (NSData *)RSAdecryptData:(NSData *)data privateKey:(NSString *)privKey{
        if(!data || !privKey){
            return nil;
        }
        SecKeyRef keyRef = [Cryptor addPrivateKey:privKey];
        if(!keyRef){
            return nil;
        }
        return [Cryptor decryptData:data withKeyRef:keyRef];
    }
    
    + (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
        const uint8_t *srcbuf = (const uint8_t *)[data bytes];
        size_t srclen = (size_t)data.length;
        
        size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
        UInt8 *outbuf = malloc(block_size);
        size_t src_block_size = block_size;
        
        NSMutableData *ret = [[NSMutableData alloc] init];
        for(int idx=0; idx<srclen; idx+=src_block_size){
            //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
            size_t data_len = srclen - idx;
            if(data_len > src_block_size){
                data_len = src_block_size;
            }
            
            size_t outlen = block_size;
            OSStatus status = noErr;
            status = SecKeyDecrypt(keyRef,
                                   kSecPaddingNone,
                                   srcbuf + idx,
                                   data_len,
                                   outbuf,
                                   &outlen
                                   );
            if (status != 0) {
                NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
                ret = nil;
                break;
            }else{
                //the actual decrypted data is in the middle, locate it!
                int idxFirstZero = -1;
                int idxNextZero = (int)outlen;
                for ( int i = 0; i < outlen; i++ ) {
                    if ( outbuf[i] == 0 ) {
                        if ( idxFirstZero < 0 ) {
                            idxFirstZero = i;
                        } else {
                            idxNextZero = i;
                            break;
                        }
                    }
                }
                
                [ret appendBytes:&outbuf[idxFirstZero+1] length:idxNextZero-idxFirstZero-1];
            }
        }
        
        free(outbuf);
        CFRelease(keyRef);
        return ret;
    }
    
    /* START: Encryption & Decryption with RSA private key */
    + (NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef isSign:(BOOL)isSign {
        const uint8_t *srcbuf = (const uint8_t *)[data bytes];
        size_t srclen = (size_t)data.length;
        
        size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
        void *outbuf = malloc(block_size);
        size_t src_block_size = block_size - 11;
        
        NSMutableData *ret = [[NSMutableData alloc] init];
        for(int idx=0; idx<srclen; idx+=src_block_size){
            //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
            size_t data_len = srclen - idx;
            if(data_len > src_block_size){
                data_len = src_block_size;
            }
            
            size_t outlen = block_size;
            OSStatus status = noErr;
            
            if (isSign) {
                status = SecKeyRawSign(keyRef,
                                       kSecPaddingPKCS1,
                                       srcbuf + idx,
                                       data_len,
                                       outbuf,
                                       &outlen
                                       );
            } else {
                status = SecKeyEncrypt(keyRef,
                                       kSecPaddingPKCS1,
                                       srcbuf + idx,
                                       data_len,
                                       outbuf,
                                       &outlen
                                       );
            }
            if (status != 0) {
                NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
                ret = nil;
                break;
            }else{
                [ret appendBytes:outbuf length:outlen];
            }
        }
        
        free(outbuf);
        CFRelease(keyRef);
        return ret;
    }
    
    + (SecKeyRef)addPublicKey:(NSString *)key{
        NSRange spos = [key rangeOfString:@"-----BEGIN PUBLIC KEY-----"];
        NSRange epos = [key rangeOfString:@"-----END PUBLIC KEY-----"];
        if(spos.location != NSNotFound && epos.location != NSNotFound){
            NSUInteger s = spos.location + spos.length;
            NSUInteger e = epos.location;
            NSRange range = NSMakeRange(s, e-s);
            key = [key substringWithRange:range];
        }
        key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
        
        // This will be base64 encoded, decode it.
        NSData *data = base64_decode(key);
        data = [Cryptor stripPublicKeyHeader:data];
        if(!data){
            return nil;
        }
        
        //a tag to read/write keychain storage
        NSString *tag = @"RSAUtil_PubKey";
        NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
        
        // Delete any old lingering key with the same tag
        NSMutableDictionary *publicKey = [[NSMutableDictionary alloc] init];
        [publicKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
        [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
        [publicKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
        SecItemDelete((__bridge CFDictionaryRef)publicKey);
        
        // Add persistent version of the key to system keychain
        [publicKey setObject:data forKey:(__bridge id)kSecValueData];
        [publicKey setObject:(__bridge id) kSecAttrKeyClassPublic forKey:(__bridge id)
         kSecAttrKeyClass];
        [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
         kSecReturnPersistentRef];
        
        CFTypeRef persistKey = nil;
        OSStatus status = SecItemAdd((__bridge CFDictionaryRef)publicKey, &persistKey);
        if (persistKey != nil){
            CFRelease(persistKey);
        }
        if ((status != noErr) && (status != errSecDuplicateItem)) {
            return nil;
        }
        
        [publicKey removeObjectForKey:(__bridge id)kSecValueData];
        [publicKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
        [publicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
        [publicKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
        
        // Now fetch the SecKeyRef version of the key
        SecKeyRef keyRef = nil;
        status = SecItemCopyMatching((__bridge CFDictionaryRef)publicKey, (CFTypeRef *)&keyRef);
        if(status != noErr){
            return nil;
        }
        return keyRef;
    }
    
    + (NSData *)stripPublicKeyHeader:(NSData *)d_key{
        // Skip ASN.1 public key header
        if (d_key == nil) return(nil);
        
        unsigned long len = [d_key length];
        if (!len) return(nil);
        
        unsigned char *c_key = (unsigned char *)[d_key bytes];
        unsigned int  idx     = 0;
        
        if (c_key[idx++] != 0x30) return(nil);
        
        if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
        else idx++;
        
        // PKCS #1 rsaEncryption szOID_RSA_RSA
        static unsigned char seqiod[] =
        { 0x30,   0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x01,
            0x01, 0x05, 0x00 };
        if (memcmp(&c_key[idx], seqiod, 15)) return(nil);
        
        idx += 15;
        
        if (c_key[idx++] != 0x03) return(nil);
        
        if (c_key[idx] > 0x80) idx += c_key[idx] - 0x80 + 1;
        else idx++;
        
        if (c_key[idx++] != '\0') return(nil);
        
        // Now make a new NSData from this buffer
        return([NSData dataWithBytes:&c_key[idx] length:len - idx]);
    }
    
    + (NSData *)stripPrivateKeyHeader:(NSData *)d_key{
        // Skip ASN.1 private key header
        if (d_key == nil) return(nil);
        
        unsigned long len = [d_key length];
        if (!len) return(nil);
        
        unsigned char *c_key = (unsigned char *)[d_key bytes];
        unsigned int  idx     = 22; //magic byte at offset 22
        
        if (0x04 != c_key[idx++]) return nil;
        
        //calculate length of the key
        unsigned int c_len = c_key[idx++];
        int det = c_len & 0x80;
        if (!det) {
            c_len = c_len & 0x7f;
        } else {
            int byteCount = c_len & 0x7f;
            if (byteCount + idx > len) {
                //rsa length field longer than buffer
                return nil;
            }
            unsigned int accum = 0;
            unsigned char *ptr = &c_key[idx];
            idx += byteCount;
            while (byteCount) {
                accum = (accum << 8) + *ptr;
                ptr++;
                byteCount--;
            }
            c_len = accum;
        }
        
        // Now make a new NSData from this buffer
        return [d_key subdataWithRange:NSMakeRange(idx, c_len)];
    }
    
    + (SecKeyRef)addPrivateKey:(NSString *)key{
        NSRange spos;
        NSRange epos;
        spos = [key rangeOfString:@"-----BEGIN RSA PRIVATE KEY-----"];
        if(spos.length > 0){
            epos = [key rangeOfString:@"-----END RSA PRIVATE KEY-----"];
        }else{
            spos = [key rangeOfString:@"-----BEGIN PRIVATE KEY-----"];
            epos = [key rangeOfString:@"-----END PRIVATE KEY-----"];
        }
        if(spos.location != NSNotFound && epos.location != NSNotFound){
            NSUInteger s = spos.location + spos.length;
            NSUInteger e = epos.location;
            NSRange range = NSMakeRange(s, e-s);
            key = [key substringWithRange:range];
        }
        key = [key stringByReplacingOccurrencesOfString:@"\r" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@"\n" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@"\t" withString:@""];
        key = [key stringByReplacingOccurrencesOfString:@" "  withString:@""];
        
        // This will be base64 encoded, decode it.
        NSData *data = base64_decode(key);
        data = [Cryptor stripPrivateKeyHeader:data];
        if(!data){
            return nil;
        }
        
        //a tag to read/write keychain storage
        NSString *tag = @"RSAUtil_PrivKey";
        NSData *d_tag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];
        
        // Delete any old lingering key with the same tag
        NSMutableDictionary *privateKey = [[NSMutableDictionary alloc] init];
        [privateKey setObject:(__bridge id) kSecClassKey forKey:(__bridge id)kSecClass];
        [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
        [privateKey setObject:d_tag forKey:(__bridge id)kSecAttrApplicationTag];
        SecItemDelete((__bridge CFDictionaryRef)privateKey);
        
        // Add persistent version of the key to system keychain
        [privateKey setObject:data forKey:(__bridge id)kSecValueData];
        [privateKey setObject:(__bridge id) kSecAttrKeyClassPrivate forKey:(__bridge id)
         kSecAttrKeyClass];
        [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)
         kSecReturnPersistentRef];
        
        CFTypeRef persistKey = nil;
        OSStatus status = SecItemAdd((__bridge CFDictionaryRef)privateKey, &persistKey);
        if (persistKey != nil){
            CFRelease(persistKey);
        }
        if ((status != noErr) && (status != errSecDuplicateItem)) {
            return nil;
        }
        
        [privateKey removeObjectForKey:(__bridge id)kSecValueData];
        [privateKey removeObjectForKey:(__bridge id)kSecReturnPersistentRef];
        [privateKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];
        [privateKey setObject:(__bridge id) kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];
        
        // Now fetch the SecKeyRef version of the key
        SecKeyRef keyRef = nil;
        status = SecItemCopyMatching((__bridge CFDictionaryRef)privateKey, (CFTypeRef *)&keyRef);
        if(status != noErr){
            return nil;
        }
        return keyRef;
    }
    
    + (NSString *)loadPubKeyWithPemName:(NSString *)pemName {
        NSString *fileName = [[NSBundle mainBundle] pathForResource:pemName ofType:@"pem"];
        NSData *certData = [NSData dataWithContentsOfFile:fileName];
        return [[NSString alloc]initWithData:certData encoding:NSUTF8StringEncoding];
    }
    
    static NSString *base64_encode_data(NSData *data){
        data = [data base64EncodedDataWithOptions:0];
        NSString *ret = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        return ret;
    }
    
    static NSData *base64_decode(NSString *str){
        NSData *data = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
        return data;
    }
    
    //data -> 16进制字符串
    + (NSString *)hexEncoding:(NSData*)data {
        const unsigned char *dataBuffer = (const unsigned char *)[data bytes];
        if (!dataBuffer) return [NSString string];
        
        NSUInteger          dataLength  = [data length];
        NSMutableString     *hexString  = [NSMutableString stringWithCapacity:(dataLength * 2)];
        
        for (int i = 0; i < dataLength; ++i)
            [hexString appendString:[NSString stringWithFormat:@"%02lx", (unsigned long)dataBuffer[i]]];
        
        return [NSString stringWithString:hexString];
    }
    
    // 16进制转NSData
    + (NSData *)hexDecoding:(NSString *)string
    {
        string = [string lowercaseString];
        NSMutableData *data= [NSMutableData new];
        unsigned char whole_byte;
        char byte_chars[3] = {'\0','\0','\0'};
        int i = 0;
        int length = string.length;
        while (i < length-1) {
            char c = [string characterAtIndex:i++];
            if (c < '0' || (c > '9' && c < 'a') || c > 'f')
                continue;
            byte_chars[0] = c;
            byte_chars[1] = [string characterAtIndex:i++];
            whole_byte = strtol(byte_chars, NULL, 16);
            [data appendBytes:&whole_byte length:1];
        }
        return data;
    }
    
    @end
    
    

    生成RSA公钥和私钥的命令,亲测ok

    openssl genrsa -out private_key.pem 1024
    openssl req -new -key private_key.pem -out rsaCertReq.csr
    openssl x509 -req -days 3650 -in rsaCertReq.csr -signkey private_key.pem -out rsaCert.crt
    openssl x509 -outform der -in rsaCert.crt -out public_key.der          // Create public_key.der For IOS
    openssl pkcs12 -export -out private_key.p12 -inkey private_key.pem -in rsaCert.crt  // Create private_key.p12 For IOS. 这一步,请记住你输入的密码,IOS代码里会用到
    openssl rsa -in private_key.pem -out rsa_public_key.pem -pubout             // Create rsa_public_key.pem For Java
    openssl pkcs8 -topk8 -in private_key.pem -out pkcs8_private_key.pem -nocrypt     // Create pkcs8_private_key.pem For Java
    

    那些年趟过的坑

    发现公司生成的密钥不是以上命令生成的,而是通过java代码生成的,并不是PKCS8,说是PKCS11,所以,上面代码公钥解密的时候,需要替换成以下方法

    + (NSData *)decryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
        const uint8_t *srcbuf = (const uint8_t *)[data bytes];
        size_t srclen = (size_t)data.length;
        
        size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
        UInt8 *outbuf = malloc(block_size);
        size_t src_block_size = block_size;
        
        NSMutableData *ret = [[NSMutableData alloc] init];
        for(int idx=0; idx<srclen; idx+=src_block_size){
            //NSLog(@"%d/%d block_size: %d", idx, (int)srclen, (int)block_size);
            size_t data_len = srclen - idx;
            if(data_len > src_block_size){
                data_len = src_block_size;
            }
            
            size_t outlen = block_size;
            OSStatus status = noErr;
            status = SecKeyDecrypt(keyRef,
                                   kSecPaddingNone,
                                   srcbuf + idx,
                                   data_len,
                                   outbuf,
                                   &outlen
                                   );
            if (status != 0) {
                NSLog(@"SecKeyEncrypt fail. Error Code: %d", status);
                ret = nil;
                break;
            }else{
                //the actual decrypted data is in the middle, locate it!
                int idxFirstZero = -1;
                int idxNextZero = (int)outlen;
                for ( int i = 0; i < outlen; i++ ) {
                    if ( outbuf[i] == 0 ) {
                        if ( idxFirstZero < 0 ) {
                            idxFirstZero = i;
                        } else {
                            idxNextZero = i;
                            break;
                        }
                    }
                }
                
                //[ret appendBytes:&outbuf[idxFirstZero+1] length:idxNextZero-idxFirstZero-1];
              [ret appendBytes:&outbuf[idxFirstZero+1] length:outlen-idxFirstZero-1];
            }
        }
        
        free(outbuf);
        CFRelease(keyRef);
        return ret;
    }
    

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