在iPhone/Objective C中生成SHA256 ...？

Question

如何在iPhone/Objective-C中创建一个字符串的SHA256？ Sha256 in Objective-C for iPhone 我已经阅读了这篇文章，但是我无法理解它。

我想要创建类似于以下PHP函数输出的结果：

$hash = hash_hmac("sha256", implode(';', $hash_parameters), $api_key);

其中hash参数是参数数组...

你能写一个方法来接受输入字符串吗？

该方法的输出将是NSData还是NSString？

我需要用这个来创建一个请求吗？

所以在请求对象中...

[theRequest setHTTPBody:requestBody];

requestBody应该是什么类型？

- Kuldeep Singh

---

这个问题在这里已经得到了明确的回答-> https://dev59.com/R3A65IYBdhLWcg3wogSe#11426583 - Jagadeeshwar

Answer 1

我不确定我完全理解你的问题，但如果你想创建一个哈希字符串，你可以将参数作为参数传递给哈希函数。

-(void)generateHashedString {

    NSString *key = @"Some random string";
    //enter your objects you want to encode in the data object
    NSString *data = [NSString stringWithFormat:@"%@%@%@", @"sha256", hash_parameters, api_key];

    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];

}

这将为您提供一个哈希字符串，您可以使用它来进行请求。 NSLog（@“％@”，hash）; 查看您生成的内容！

还要确保您导入#import <CommonCrypto / CommonHMAC.h>

- TALLBOY

---

这是base64编码。如果您不需要它，可以省略base64编码。 - TALLBOY

那么我该如何将HMAC转换为NSString类型？ - Maysam Torabi

我对解决方案也很感兴趣，base64编码我想这是一个未记录的功能，而且结果也不好。我正在尝试这个，但效果也不好：NSString *str = [[NSString alloc] initWithData:HMAC encoding:NSASCIIStringEncoding]; - Cristi Băluță

运行得很好。我添加了iOS7> base64编码，如下所示：NSString *hash = [HMAC base64EncodedStringWithOptions:0]; 一切都很顺利。谢谢@TALLBOY - elliotrock

Answer 2

我没有将以下代码与PHP函数输出进行比较，但它对我有效：

+(NSString *)signWithKey:(NSString *)key usingData:(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)];

    return [[HMAC.description stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"<>"]] stringByReplacingOccurrencesOfString:@" " withString:@""];
}

如果有帮助，请告诉我...

- der_michael

Answer 3

我花了一整天的时间，试图将生成的哈希（字节）转换为可读数据。我使用了像上面答案中提到的base64编码，但对我来说根本不起作用（顺便说一下，你需要一个外部.h文件才能使用base64编码，我有一个）。所以我做的是这个（没有外部.h文件也能完美工作）：

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

// Now convert to NSData structure to make it usable again
NSData *out = [NSData dataWithBytes:cHMAC length:CC_SHA256_DIGEST_LENGTH];

// description converts to hex but puts <> around it and spaces every 4 bytes
NSString *hash = [out description];
hash = [hash stringByReplacingOccurrencesOfString:@" " withString:@""];
hash = [hash stringByReplacingOccurrencesOfString:@"<" withString:@""];
hash = [hash stringByReplacingOccurrencesOfString:@">" withString:@""];
// hash is now a string with just the 40char hash value in it
NSLog(@"%@",hash);

- bruno

Answer 4

作为参考，这个HMac哈希将在PHP上工作。

- (NSString *)getToken:(NSString *)queryString
{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]];
    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSString *dateString = [formatter stringFromDate:[NSDate date]];
    NSDate *dateTodayUTC = [formatter dateFromString:dateString];
    NSString *nowTimestamp = [NSString stringWithFormat:@"%.f", [dateTodayUTC timeIntervalSince1970]];

    NSString *hashCombinations = [[NSString alloc] initWithFormat:@"%@%@%.f", queryString, public_api_key, [dateTodayUTC timeIntervalSince1970]];

    const char *privateKey  = [private_api_key cStringUsingEncoding:NSUTF8StringEncoding];
    const char *requestData = [hashCombinations cStringUsingEncoding:NSUTF8StringEncoding];
    unsigned char cHMAC[CC_SHA256_DIGEST_LENGTH];

    //HmacSHA256
    CCHmac(kCCHmacAlgSHA256, // algorithm
           privateKey, strlen(privateKey), // privateKey
           requestData, strlen(requestData), // requestData
           cHMAC); // length

    NSString *hash;
    NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
    for(int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++)
        [output appendFormat:@"%02x", cHMAC[i]];
    hash = output;

    NSString *base64HashString = [self base64String:hash];
    self.tokenLabel.text = hash;

    NSLog(@"generated hash = %@", hash);
    NSLog(@"base64 hash = %@", base64HashString);
    NSLog(@"timestamp = %@ nsdate utc = %@", nowTimestamp, dateString);
    NSLog(@"combinations %@", hashCombinations);
    return [base64HashString urlencode];
}

您可以使用这个Base64方法。

- (NSString *)base64String:(NSString *)str
{
    NSData *theData = [str dataUsingEncoding: NSASCIIStringEncoding];
    const uint8_t* input = (const uint8_t*)[theData bytes];
    NSInteger length = [theData length];

    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
    uint8_t* output = (uint8_t*)data.mutableBytes;

    NSInteger i;
    for (i=0; i < length; i += 3) {
        NSInteger value = 0;
        NSInteger j;
        for (j = i; j < (i + 3); j++) {
            value <<= 8;

            if (j < length) {
                value |= (0xFF & input[j]);
            }
        }

        NSInteger theIndex = (i / 3) * 4;
        output[theIndex + 0] =                    table[(value >> 18) & 0x3F];
        output[theIndex + 1] =                    table[(value >> 12) & 0x3F];
        output[theIndex + 2] = (i + 1) < length ? table[(value >> 6)  & 0x3F] : '=';
        output[theIndex + 3] = (i + 2) < length ? table[(value >> 0)  & 0x3F] : '=';
    }

    return [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
}

- John Paul Manoza

Answer 5

我认为这是更紧凑的解决方案：

#import <CommonCrypto/CommonCrypto.h>

...

-(NSData*)Sha256WithKey:(NSData*)key andData:(NSData*)data{
     NSMutableData* result = [NSMutableData 
                               dataWithCapacity:CC_SHA256_DIGEST_LENGTH];

     CCHmac(kCCHmacAlgSHA256, [key bytes], [key length],
            [data bytes], [data length], result.mutableBytes);

     return result;
 }
 ....

- Denis Kreshikhin