gistfile1.m

//  CryptoViewController.m

#import "CryptoViewController.h"
#import <CommonCrypto/CommonCryptor.h>

@interface NSData (Crypto)
- (NSData *) cipher: (CCOperation) operation withKey: (NSData *) key;
- (NSData *) cipherUsingAES128: (NSData *) key;
- (NSData *) decipherUsingAES128: (NSData *) key;
@end

@implementation NSData (Crypto)

- (NSData *) cipherUsingAES128: (NSData *) key {
        return [self cipher: kCCEncrypt withKey: key];

}

- (NSData *) decipherUsingAES128: (NSData *) key {
        return [self cipher: kCCDecrypt withKey: key];
}

- (NSData *) cipher: (CCOperation) operation withKey: (NSData *) key
{
       int plainTextBlockSize = ([self length] + kCCBlockSizeAES128) & ~(kCCBlockSizeAES128 - 1);

       unsigned char plainText[plainTextBlockSize];
       bzero(plainText, plainTextBlockSize);

       size_t plainTextLength;


       CCCryptorStatus status = CCCrypt(operation,
               kCCAlgorithmAES128,
               kCCOptionECBMode,
               [key bytes],
               kCCKeySizeAES128,
               NULL,
               [self bytes],
               [self length],
               plainText,
               plainTextBlockSize,
               &plainTextLength
       );

       if (status == kCCSuccess) {
               return [NSData dataWithBytes: plainText length: plainTextLength];
       } else {
               return nil;
       }
}

@end

@implementation CryptoViewController

- (void) testWithData: (NSData*) plain
{
	NSData* key = [NSData dataWithBytes: "0123456789abcdef" length: 16];
	
	NSData* encrypted = [plain cipherUsingAES128: key];
	NSData* decrypted = [encrypted decipherUsingAES128: key];

	NSLog(@"  Original  length = %d", [plain length]);
	NSLog(@"  Encrypted length = %d", [encrypted length]);
	NSLog(@"  Decrypted length = %d", [decrypted length]);
	
	if ([plain length] != [decrypted length]) {
		NSLog(@"    Fail");
	}
}

- (void) viewDidLoad
{
	NSLog(@"Testing with content shorter than the block size");
	[self testWithData: [NSData dataWithBytes: "Hi!" length: 3]];

	NSLog(@"Testing with content equal to the block size");
	[self testWithData: [NSData dataWithBytes: "01234567890abcdef" length: 16]];

	NSLog(@"Testing with content equal to a multiple block size");
	[self testWithData: [NSData dataWithBytes: "01234567890abcdef01234567890abcdef01234567890abcdef" length: 3*16]];

	NSLog(@"Testing with content longer than the block size");
	[self testWithData: [NSData dataWithBytes: "This plaintext is longer than the block size" length: 44]];
}

@end