Objective-C sample code for HMAC-SHA1

Question

I need to generate HMAC-SHA1 in Objective C. But i didnt find anything that works. I tried with CommonCrypto, using CCHMAC, but didnt works. I need to generate a hmac and after generate HOTP number.

Somebody have any example code in Objective C or C?

Answer 1

Here's how you generate an HMAC using SHA-256:

NSString *key;
NSString *data;

const char *cKey  = [key cStringUsingEncoding:NSASCIIStringEncoding];
const char *cData = [data cStringUsingEncoding:NSASCIIStringEncoding];

unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];

CCHmac(kCCHmacAlgSHA256, cKey, strlen(cKey), cData, strlen(cData), cHMAC);

NSData *HMAC = [[NSData alloc] initWithBytes:cHMAC
                                      length:sizeof(cHMAC)];

NSString *hash = [HMAC base64Encoding];

I'm not aware of an HOTP library, but the algorithm was quite simple, if I recall correctly.