Use the HMAC-SHA1 signature algorithm as defined by the [RFC2104] to sign the request where text is the Signature Base String and key is the concatenated values of the Consumer Secret and Access Secret separated by an ‘&’ character (show ‘&’ even if Access Secret is empty as some methods do not require an Access Token).

The calculated digest octet string,first base64-encoded per [RFC2045],then escaped using the [RFC3986] percent-encoding (%xx) mechanism is the oauth_signature.

对于base64编码,我使用了QSStrings.h

我编码的步骤如下：

- (void)viewDidLoad
{
NSTimeInterval intervalFloat = [[NSDate date] timeIntervalSince1970];
int interval = (int) intervalFloat;
NSLog(@"time interval: %d",interval);

//for oauth_nonce random string
NSString *randomString = [self genRandString]; //see definition below
NSLog(@"%@",randomString);

NSString *requestString = [NSString stringWithFormat:@"POST&http%3A%2F%2Fplatform.fatsecret.com%2Frest%2Fserver.api&format%3Djson%26method%3Dprofile.create%26oauth_consumer_key%3Db753c99ccxxxxxx%26oauth_nonce%3D%@%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D%d%26oauth_version%3D1.0",randomString,interval];
NSString *secret = @"3959096c04xxxxxxxx&";

NSString *encodedStr = [self hmacsha1:requestString secret:secret]; //see definition below
NSLog(@"encodedStr: %@",encodedStr);

NSString *encodedString = [self urlEncodeValue:encodedStr]; //see definition below
NSLog(@"encodedString: %@",encodedString);

NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://platform.fatsecret.com/rest/server.api?format=json&method=profile.create&oauth_consumer_key=b753c99ccxxxxxx&oauth_nonce=%@&oauth_signature=%@&oauth_signature_method=HMAC-SHA1&oauth_timestamp=%d&oauth_version=1.0",encodedString,interval]];

_request = [ASIFormDataRequest requestWithURL:url];
[_request setPostValue:@"json" forKey:@"format"];
[_request setPostValue:@"profile.create" forKey:@"method"];
[_request setPostValue:@"b753c99ccxxxxxx" forKey:@"oauth_consumer_key"];
[_request setPostValue:randomString forKey:@"oauth_nonce"];
[_request setPostValue:encodedString forKey:@"oauth_signature"];
[_request setPostValue:@"HMAC-SHA1" forKey:@"oauth_signature_method"];
[_request setPostValue:[NSNumber numberWithInt:interval] forKey:@"oauth_timestamp"];
[_request setPostValue:@"1.0" forKey:@"oauth_version"];

[_request setDelegate:self];
_request.timeOutSeconds = 60.0; 
[_request startAsynchronous];

}

我在上面的代码中使用的方法的定义如下：

- (NSString *)hmacsha1:(NSString *)data secret:(NSString *)key {

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

unsigned char cHMAC[CC_SHA1_DIGEST_LENGTH];

CCHmac(kCCHmacAlgSHA1,cKey,strlen(cKey),cData,strlen(cData),cHMAC);

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

NSString *hash = [QSStrings encodeBase64WithData:HMAC];

NSLog(@"Hash: %@",hash);  

return hash;
}

NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

-(NSString *) genRandString {
//fixing length of 4 chars
NSMutableString *randomString = [NSMutableString stringWithCapacity: 4];

for (int i=0; i<4; i++) {
    [randomString appendFormat: @"%C",[letters characterAtIndex: arc4random() % [letters length]]];
}

return randomString;
}

- (NSString *)urlEncodeValue:(NSString *)str
{
NSMutableString * output = [NSMutableString string];
const unsigned char * source = (const unsigned char *)[str UTF8String];
int sourceLen = strlen((const char *)source);
for (int i = 0; i < sourceLen; ++i) {
    const unsigned char thisChar = source[i];
    if (thisChar == ' '){
        [output appendString:@"+"];
    } else if (thisChar == '.' || thisChar == '-' || thisChar == '_' || thisChar == '~' || 
               (thisChar >= 'a' && thisChar <= 'z') ||
               (thisChar >= 'A' && thisChar <= 'Z') ||
               (thisChar >= '0' && thisChar <= '9')) {
        [output appendFormat:@"%c",thisChar];
    } else {
        [output appendFormat:@"%%%02X",thisChar];
    }
}
return output;
}

您可以通过从here下载我的项目来查看问题