Implementation of AES encryption on iOS

Encryption. h file
 
 
 
 
 
# Import <Foundation/Foundation. h>
 
 
 
@ Class NSString;
 
 
 
@ Interface NSData (Encryption)
 
 
 
-(NSData *) AES256EncryptWithKey :( NSString *) key; // Encryption
 
-(NSData *) AES256DecryptWithKey :( NSString *) key; // decrypt
 
-(NSString *) newStringInBase64FromData; // append 64 Encoding
 
+ (NSString *) base64encode :( NSString *) str; // same as the preceding 64 Encoding
 
 
 
@ End
 
 
 
Bytes ------------------------------------------------------------------------------------------------
 
 
 
Encryption. m file
 
 
 
# Import "Encryption. h"
 
# Import <CommonCrypto/CommonCryptor. h>
 
 
 
 
 
Static char base64 [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 + /";
 
 
 
@ Implementation NSData (Encryption)
 
 
 
-(NSData *) AES256EncryptWithKey :( NSString *) key // Encryption
 
{
 
Char keyPtr [kCCKeySizeAES256 + 1];
 
Bzero (keyPtr, sizeof (keyPtr ));
 
[Key getCString: keyPtr maxLength: sizeof (keyPtr) encoding: NSUTF8StringEncoding];
 
NSUInteger dataLength = [self length];
 
Size_t bufferSize = dataLength + kCCBlockSizeAES128;
 
Void * buffer = malloc (bufferSize );
 
Size_t numBytesEncrypted = 0;
 
CCCryptorStatus cryptStatus = CCCrypt (kCCEncrypt, kCCAlgorithmAES128,
 
KCCOptionPKCS7Padding | kCCOptionECBMode,
 
KeyPtr, kCCBlockSizeAES128,
 
NULL,
 
[Self bytes], dataLength,
 
Buffer, bufferSize,
 
& NumBytesEncrypted );
 
If (cryptStatus = kCCSuccess ){
 
Return [NSData dataWithBytesNoCopy: buffer length: numBytesEncrypted];
 
}
 
Free (buffer );
 
Return nil;
 
}
 
 
 
 
 
-(NSData *) AES256DecryptWithKey :( NSString *) key // decryption
 
{
 
Char keyPtr [kCCKeySizeAES256 + 1];
 
Bzero (keyPtr, sizeof (keyPtr ));
 
[Key getCString: keyPtr maxLength: sizeof (keyPtr) encoding: NSUTF8StringEncoding];
 
NSUInteger dataLength = [self length];
 
Size_t bufferSize = dataLength + kCCBlockSizeAES128;
 
Void * buffer = malloc (bufferSize );
 
Size_t numBytesDecrypted = 0;
 
CCCryptorStatus cryptStatus = CCCrypt (kCCDecrypt, kCCAlgorithmAES128,
 
KCCOptionPKCS7Padding | kCCOptionECBMode,
 
KeyPtr, kCCBlockSizeAES128,
 
NULL,
 
[Self bytes], dataLength,
 
Buffer, bufferSize,
 
& NumBytesDecrypted );
 
If (cryptStatus = kCCSuccess ){
 
Return [NSData dataWithBytesNoCopy: buffer length: numBytesDecrypted];
 
}
 
Free (buffer );
 
Return nil;
 
}
 
 
 
 
 
-(NSString *) newStringInBase64FromData // append 64 Encoding
 
{
 
NSMutableString * dest = [[NSMutableString alloc] initWithString: @ ""];
 
Unsigned char * working = (unsigned char *) [self bytes];
 
Int srcLen = [self length];
 
For (int I = 0; I <srcLen; I + = 3 ){
 
For (int nib = 0; nib <4; nib ++ ){
 
Int byt = (nib = 0 )? 0: nib-1;
 
Int ix = (nib + 1) * 2;
 
If (I + byt> = srcLen) break;
 
Unsigned char curr = (working [I + byt] <(8-ix) & 0x3F );
 
If (I + nib <srcLen) curr | = (working [I + nib]> ix) & 0x3F );
 
[Dest appendFormat: @ "% c", base64 [curr];
 
}
 
}
 
Return dest;
 
}
 
 
 
+ (NSString *) base64encode :( NSString *) str
 
{
 
If ([str length] = 0)
 
Return @"";
 
Const char * source = [str UTF8String];
 
Int strlength = strlen (source );
 
Char * characters = malloc (strlength + 2)/3) * 4 );
 
If (characters = NULL)
 
Return nil;
 
NSUInteger length = 0;
 
NSUInteger I = 0;
 
While (I <strlength ){
 
Char buffer [3] = {0, 0 };
 
Short bufferLength = 0;
 
While (bufferLength <3 & I <strlength)
 
Buffer [bufferLength ++] = source [I ++];
 
Characters [length ++] = base64 [(buffer [0] & 0xFC)> 2];
 
Characters [length ++] = base64 [(buffer [0] & 0x03) <4) | (buffer [1] & 0xF0)> 4)];
 
If (bufferLength> 1)
 
Characters [length ++] = base64 [(buffer [1] & 0x0F) <2) | (buffer [2] & 0xC0)> 6)];
 
Else characters [length ++] = ';
 
If (bufferLength> 2)
 
Characters [length ++] = base64 [buffer [2] & 0x3F];
 
Else characters [length ++] = ';
 
}
 
NSString * g = [[NSString alloc] initWithBytesNoCopy: characters length: length encoding: NSASCIIStringEncoding freeWhenDone: YES] autorelease];
 
Return g;
 
}
 
 
 
 
 
@ End
 
 
 
Bytes ------------------------------------------------------------------------------------------------
 
 
 
Test code
 
 
 
 
 
# Import "Encryption. h"
 
 
 
 
 
 
 
 
 
NSString * key = @ "my password ";
 
NSString * secret = @ "text to encrypt ";
 
// Encryption
 
NSData * plain = [secret dataUsingEncoding: NSUTF8StringEncoding];
 
NSData * cipher = [plain AES256EncryptWithKey: key];
 
NSLog (@ "% @", [[cipher newStringInBase64FromData] autorelease]);
 
Printf ("% s \ n", [[cipher description] UTF8String]);
 
NSLog (@ "% @", [[[NSString alloc] initWithData: cipher encoding: NSUTF8StringEncoding] autorelease]); // print out null because no decryption is performed.
 
// Decrypt
 
Plain = [cipher AES256DecryptWithKey: key];
 
Printf ("% s \ n", [[plain description] UTF8String]);
 
NSLog (@ "% @", [[[NSString alloc] initWithData: plain encoding: NSUTF8StringEncoding] autorelease]);
// Print the secret and use the password to decrypt it. If the wrong password is used, null is printed.

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