How to use the CCHmac() function in iOS

Question

CCHmac(CCHmacAlgorithm algorithm, const void *key, size_t keyLength,
       const void *data, size_t dataLength, void *macOut);

For example, I have API:

https://
somedomain/
beta/
men?
key=[API KEY]&signature=[Signature]}

How can I pass API key to CCHmac function and get the signature and make the complete API, e.g.:

https://
Somedomain/
beta/
men?
key="Abcdefghi12345"&signature=jhfjkshkjfhsdkfhkshdkjfioeoiejafjnanjasbjfs="}

Can someone provide me good tutorial or sample code for CCHmac function? I looked on the web but I don't find anything.

Not sure if this is considered a duplicate, but a good start is here: http://stackoverflow.com/q/756492/620197 — Mike D, Aug 28 '14 at 21:19
I already saw this link. I want to understand how this things works ? — user3908542, Aug 28 '14 at 21:33

score 1 · Answer 1 · answered Jan 16 '15 at 07:55

CCHmacAlgorithm algorithm - set HMAC algorithm, for example, kCCHmacAlgSHA256;

const void *key - it's your API key (I recommend use a key-stretching function called PBKDF2 previously);

size_t keyLength - const, for example, kCCKeySizeAES128;

const void *data - some additional data, for example NSString;

size_t dataLength length of data;

void *macOut - returned hash. You can save it:

uint8_t hmac[CC_SHA256_DIGEST_LENGTH] = {0}; //Call CCHmac NSData *hmacData = [NSData dataWithBytes: hmac length: CC_SHA256_DIGEST_LENGTH];

Check code from this tutorial.

1 Answers1