NSDate+AES

NSDate+AES.h

#import <Foundation/Foundation.h>

@interface NSData (AES)

- (NSData *)AES256EncryptWithPassphrase:(NSString *)pass;
- (NSData *)AES256DecryptWithPassphrase:(NSString *)pass;

@end

NSDate+AES.m

#import "NSData+AES.h"
#import <CommonCrypto/CommonCryptor.h>
#import <CommonCrypto/CommonDigest.h>

#define kDictKey            @"key"
#define kDictIv             @"iv"
#define kIterationCount     2048

@implementation NSData(AES)

- (NSData *)AES256EncryptWithPassphrase:(NSString *)pass
{
    return [self AES256Operation:kCCEncrypt passphrase:pass];
}

- (NSData *)AES256DecryptWithPassphrase:(NSString *)pass
{
    return [self AES256Operation:kCCDecrypt passphrase:pass];
}

- (NSData *)AES256Operation:(CCOperation)operation passphrase:(NSString *)pass
{
    // generate key and iv
    NSDictionary *keyIv = [NSData generateKeyIvFromPass:[pass dataUsingEncoding:NSUTF8StringEncoding]
                                                   salt:nil
                                         iterationCount:kIterationCount];

    // key
    NSData *key = keyIv[kDictKey];
    Byte *keyByte = (Byte *)malloc(key.length);
    memcpy(keyByte, key.bytes, key.length);
    
    // IV
    NSData *iv = keyIv[kDictIv];
    Byte *ivByte = (Byte *)malloc(iv.length);
    memcpy(ivByte, iv.bytes, iv.length);
    
    // out
    NSUInteger dataLen = [self length];
    size_t bufferSize = dataLen + kCCKeySizeAES256;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(operation,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding,
                                          keyByte,
                                          kCCKeySizeAES256,
                                          ivByte,
                                          self.bytes,
                                          dataLen,
                                          buffer,
                                          bufferSize,
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    free(buffer);
    return nil;
}

+ (NSDictionary *)generateKeyIvFromPass:(NSData *)pass
                                   salt:(NSData *)salt
                         iterationCount:(NSInteger)count
{
    int ivLen = kCCBlockSizeAES128;
    int keyLen = kCCKeySizeAES256;
    int keyIvLen = ivLen + keyLen;
    
    NSMutableData *keyIv = [NSMutableData new];
    NSMutableData *buff  = [NSMutableData new];
    
    while (keyIv.length < keyIvLen) {
        [buff appendData:pass];
        if (salt) [buff appendData:salt];
        
        for (int i = 0; i < count; i++) {
            buff.data = [buff MD5Digest];
        }
        [keyIv appendData:buff];
    }
    
    NSData* key = [keyIv subdataWithRange:NSMakeRange(0, keyLen)];
    NSData* iv  = [keyIv subdataWithRange:NSMakeRange(keyLen, ivLen)];
    return @{kDictKey:key, kDictIv:iv};
}

- (NSData *)MD5Digest
{
    unsigned char md5Buff[CC_MD5_DIGEST_LENGTH];
    CC_MD5(self.bytes, self.length, md5Buff);
    return [NSData dataWithBytes:(const void *)md5Buff length:sizeof(unsigned char)*CC_MD5_DIGEST_LENGTH];
}

@end