AES/cbc/pkcs5padding encription IOS - ios

Question

I have used AES algorithm for encryption in android.
The following code we have used for encryption.
String seed = "somekey";
Key key = null;
// 128 bit key
byte[] byteKey = seed.substring(0, 16).getBytes("UTF-8");
key = new SecretKeySpec(byteKey, "AES");
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(
new byte[16]));
byte[] encValue = cipher.doFinal(pValue.getBytes());
encryptedText = new BASE64Encoder().encode(encValue);
Can any one please provide the above logic for IOS.
Thanking in Advance.

Answer 1

It works both on android with:
#define FBENCRYPT_KEY_SIZE kCCKeySizeAES128
instead:
#define FBENCRYPT_KEY_SIZE kCCKeySizeAES256

Answer 2

You can use the following snippet as start point:
+ (NSData*)encryptData:(NSData*)data key:(NSData*)key iv:(NSData*)iv;
{
NSData* result = nil;
// setup key
unsigned char cKey[FBENCRYPT_KEY_SIZE];
bzero(cKey, sizeof(cKey));
[key getBytes:cKey length:FBENCRYPT_KEY_SIZE];
// setup iv
char cIv[FBENCRYPT_BLOCK_SIZE];
bzero(cIv, FBENCRYPT_BLOCK_SIZE);
if (iv) {
[iv getBytes:cIv length:FBENCRYPT_BLOCK_SIZE];
}
// setup output buffer
size_t bufferSize = [data length] + FBENCRYPT_BLOCK_SIZE;
void *buffer = malloc(bufferSize);
// do encrypt
size_t encryptedSize = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
FBENCRYPT_ALGORITHM,
kCCOptionPKCS7Padding,
cKey,
FBENCRYPT_KEY_SIZE,
cIv,
[data bytes],
[data length],
buffer,
bufferSize,
&encryptedSize);
if (cryptStatus == kCCSuccess) {
result = [NSData dataWithBytesNoCopy:buffer length:encryptedSize];
} else {
free(buffer);
NSLog(#"[ERROR] failed to encrypt|CCCryptoStatus: %d", cryptStatus);
}
return result;
}
+ (NSData*)decryptData:(NSData*)data key:(NSData*)key iv:(NSData*)iv;
{
NSData* result = nil;
// setup key
unsigned char cKey[FBENCRYPT_KEY_SIZE];
bzero(cKey, sizeof(cKey));
[key getBytes:cKey length:FBENCRYPT_KEY_SIZE];
// setup iv
char cIv[FBENCRYPT_BLOCK_SIZE];
bzero(cIv, FBENCRYPT_BLOCK_SIZE);
if (iv) {
[iv getBytes:cIv length:FBENCRYPT_BLOCK_SIZE];
}
// setup output buffer
size_t bufferSize = [data length] + FBENCRYPT_BLOCK_SIZE;
void *buffer = malloc(bufferSize);
// do decrypt
size_t decryptedSize = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
FBENCRYPT_ALGORITHM,
kCCOptionPKCS7Padding,
cKey,
FBENCRYPT_KEY_SIZE,
cIv,
[data bytes],
[data length],
buffer,
bufferSize,
&decryptedSize);
if (cryptStatus == kCCSuccess) {
result = [NSData dataWithBytesNoCopy:buffer length:decryptedSize];
} else {
free(buffer);
NSLog(#"[ERROR] failed to decrypt| CCCryptoStatus: %d", cryptStatus);
}
return result;
}
Constants
#define FBENCRYPT_ALGORITHM kCCAlgorithmAES128
#define FBENCRYPT_BLOCK_SIZE kCCBlockSizeAES128
#define FBENCRYPT_KEY_SIZE kCCKeySizeAES256
For more information, see FBEncryptor
Hope this helps.

Answer 3

Since AES has a bock size of 16-bytes PKCS#7Padding is required. Some earlier AES library implementers specified PKCS#5Padding in error.
PKCS#5Padding is only specified for a block size up to 8-bytes and PKCS#7Padding is specified for a block size up to 255-bytes. See Wikipedia: Padding. IOW PKCS#7Padding can be used in place of PKCS#5Padding.