AES 128 Encryption

gistfile1.m

//
//  NSData+AES.m
//  AESTest
//
//  Created by Oliver Drobnik on 19.12.12.
//  Copyright (c) 2012 Oliver Drobnik. All rights reserved.
//

#import "NSData+AES.h"

#import <CommonCrypto/CommonCryptor.h>

@implementation NSData (AES)

- (NSData *)AES128EncryptWithKey:(NSString*)key {
  // 'key' should be 32 bytes for AES256, will be null-padded otherwise
	char keyPtr[kCCKeySizeAES128 + 1]; // room for terminator (unused)
	bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
	
	// fetch key data
	[key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
	
	NSUInteger dataLength = [self length];
	
	//See the doc: For block ciphers, the output size will always be less than or
	//equal to the input size plus the size of one block.
	//That's why we need to add the size of one block here
	size_t bufferSize           = dataLength + kCCBlockSizeAES128;
	void* buffer                = malloc(bufferSize);
	
	size_t numBytesEncrypted    = 0;
	CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
													  keyPtr, kCCKeySizeAES256,
													  NULL /* initialization vector (optional) */,
													  [self bytes], dataLength, /* input */
													  buffer, bufferSize, /* output */
													  &numBytesEncrypted);
	
	if (cryptStatus == kCCSuccess)
	{
		//the returned NSData takes ownership of the buffer and will free it on deallocation
		return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
	}
	
	free(buffer); //free the buffer;
	return nil;
}

- (NSString *)hexString
{
	NSMutableString *tmpString = [NSMutableString string];
	
	const char *p = [self bytes];
	
	for (int i=0; i<[self length]; i++)
	{
		[tmpString appendFormat:@"%02x", (unsigned char)p[i]];
	}
	
	return [tmpString uppercaseString];
}

@end