Implementing Base 64 and SHA

Question

I have tried following code so far:

+(NSString*)encodeString:(NSString*)origString{
    /* Here we can choose the algorithm */
    NSData *keyData = [@"secret_key" dataUsingEncoding:NSUTF8StringEncoding];

    NSData *textData = [origString dataUsingEncoding:NSUTF8StringEncoding];
    uint8_t digest[CC_SHA1_DIGEST_LENGTH] = {0};

    CCHmacContext hmacContext;
    CCHmacInit(&hmacContext, kCCHmacAlgSHA1, keyData.bytes, keyData.length);
    CCHmacUpdate(&hmacContext, textData.bytes, textData.length);
    CCHmacFinal(&hmacContext, digest);

    /* out is HMAC */
    NSData *out = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];

    /* resultString is Base64 encoded HMAC */
    NSString *resultString = [out base64EncodedString];
    return resultString;
}

This is giving correct result as wanted. But my android and Back-end partner want me to clone following code into objective-c:

private String encryptString(String origString) {
    String encryptedString = "";
    Cipher cipher = null;
    byte[] encoded = null;
    byte[] rawEnc =null;
    try {
        //Code which is working
        cipher = Cipher.getInstance("AES/CBC/PKCS5Padding", "SunJCE");
        SecretKeySpec key = new SecretKeySpec(SECRET_KEY.getBytes("UTF-8"), "AES");
        cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(INITIALIZATIO_VECTOR.getBytes("UTF-8")));
        rawEnc = cipher.doFinal(origString.getBytes("UTF-8"));
        encoded = Base64.encodeBase64(rawEnc);
        encryptedString = new String(encoded, "UTF-8");

    } catch (NoSuchAlgorithmException e) {
        System.out.println("No Such Algorithm Exception:" + e.getMessage());
    } catch (NoSuchProviderException e) {
        System.out.println("No Such Provider Exception:" + e.getMessage());
    } catch (NoSuchPaddingException e) {
        System.out.println("No Such Padding Exception:" + e.getMessage());
    } catch (InvalidKeyException | InvalidAlgorithmParameterException
             | UnsupportedEncodingException e) {
        System.out.println("Exception:" + e.getMessage());
    } catch (Exception e) {
        System.out.println("Exception:" + e.getMessage());
    }
    return encryptedString;
}
private static final String SECRET_KEY = "secret_key";
private static final String INITIALIZATIO_VECTOR = "123456";

}

And android's output is different than iOS and is as required by back-end developer. So, I have to convert code according to theirs.

The only things differs is INITIALIZATIO_VECTOR.

I want above code in objective-C.

If "The only things differs is INITIALIZATIO_VECTOR" you will need to use the same iv. Also, the key and iv should be the correct size for the encryption functions or thery will pad with *something*, that is never a good idea. BTW, generally it is just easier to use the single-shot `CCHmac` function, see this [SO answer](http://stackoverflow.com/a/30389207/451475), you would have to substitute `kCCHmacAlgSHA1` (SHA1 should no longer be used) andadd BASE64 encoding. — zaph, Sep 12 '15 at 14:03
You need to make a good attempt to write the code, if you have trouble post it here, SO does not translate code. There are several examples on SO, check them out. Hints: use the exact lengths for the key and iv. PKCS7Padding is a the same as PKCS5Padding but by definition supports larger block sizes. Note that the Java will automatically decide in a key size (somewhat scary) and for iOS you must specify a 128, 192 or 256 bit key size. — zaph, Sep 12 '15 at 15:04
@zaph - Glad you hear such a kind/helpful response...is kCCHmacAlgSHA1 is also available for android!? — Bista, Sep 12 '15 at 15:52
`kCCHmacAlgSHA1` is a Common Crypto constant, I suspect it is different on Droid. But don't use HMac SHA1, use Hmac SHA256 at a minimum if you have a choice. Also do not use text as a key, if you do have to use a string then use PBKFD2 to create a key from it. The above only applies if security is important, if not do whatever. — zaph, Sep 12 '15 at 17:16

score 1 · Answer 1 · answered Sep 12 '15 at 17:26

The question contains: "Implementing Base 64".

There is no need on iOS, just use the Apple NSData Base64 APIs:

Create a Base-64 encoded NSString from the receiver's contents using the given options:

- base64EncodedStringWithOptions:

Returns a data object initialized with the given Base-64 encoded data:

- initWithBase64EncodedData:options:

Returns a data object initialized with the given Base-64 encoded string:

- initWithBase64EncodedString:options:

etc.

Implementing Base 64 and SHA

1 Answers1