iPhone and HMAC-SHA-1 encoding

Question

im trying to get a call to amazon web service and im stuck on getting the signature, looked at this but i still have a question on it.

using this example what is th

Answer 1

// This is my code used in my Twitter connection, and working well for me.
// KeithF's code was a big help!
//
// This is a category added to NSData.

@implementation NSData (EOUtil)
- (NSData*)dataByHmacSHA1EncryptingWithKey:(NSData*)key
{   
    void* buffer = malloc(CC_SHA1_DIGEST_LENGTH);
    CCHmac(kCCHmacAlgSHA1, [key bytes], [key length], [self bytes], [self length], buffer);
    return [NSData dataWithBytesNoCopy:buffer length:CC_SHA1_DIGEST_LENGTH freeWhenDone:YES];
}
@end