如何使用SWIFT 4创建HMAC MD5十六进制签名？

Question

I'm trying to create a HMAC MD5 Hex signature using SWIFT 4.

We'll use a sample string -> "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec non metus erat. Nam nec dolor ut neque suscipit viverra in sit amet odio. Cras eleifend sed risus eget luctus"

a sample key -> "6fa9b1de89d0707f6dc952349166bbe7"

The result in my code is "dd2cef2b06ddb08e16c32a4ddc583d11"

The result on most websites is "dd2cef2b06ddb08e16c32a4ddc583d11"

The result on Cryptii.com is "7eda9d3c1356402e6fce39af3bc8d195"

The payment handler uses the exact signature from Cryptii.com as reference and I cannot generate it in iOS, using swift 4. I used the CryptoSwift library and others( https://gist.github.com/MihaelIsaev/f913d84b918d2b2c067d , Implementing HMAC and SHA1 encryption in swift ).

I use this code (from CryptoSwift):

let keyArr: Array<UInt8> = Array(key.utf8) 
let stringArr: Array<UInt8> = Array(string.utf8) 
do { 
let a = HMAC.init(key: keyArr, variant: .md5) 
let encrypted3 = try a.authenticate(stringArr) 
print("Encrypted string: (encrypted3.toHexString())") 
} catch { } 

Any ideas?

Thanks!

The android implementation looks like this and it works:

private String getFpHash(String source, String secretKey) {
    try {
        Mac mac = Mac.getInstance("HmacMD5");
        byte[] hexKeyBytes = HexEncoder.toBytesFromHex(secretKey);
        mac.init(new SecretKeySpec(hexKeyBytes, "HmacMD5"));
        String hexEncoded = HexEncoder.toHexFromBytes(mac.doFinal(source.getBytes()));
        return hexEncoded;
    }
    catch (Exception e) {
        return null;
    }
}

public class HexEncoder
{
   public static final String[] HEX_TABLE = new String[]{
            "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0a", "0b", "0c", "0d", "0e", "0f",
            "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "1a", "1b", "1c", "1d", "1e", "1f",
            "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "2a", "2b", "2c", "2d", "2e", "2f",
            "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3a", "3b", "3c", "3d", "3e", "3f",
            "40", "41", "42", "43", "44", "45", "46", "47", "48", "49", "4a", "4b", "4c", "4d", "4e", "4f",
            "50", "51", "52", "53", "54", "55", "56", "57", "58", "59", "5a", "5b", "5c", "5d", "5e", "5f",
            "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6a", "6b", "6c", "6d", "6e", "6f",
            "70", "71", "72", "73", "74", "75", "76", "77", "78", "79", "7a", "7b", "7c", "7d", "7e", "7f",
            "80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "8a", "8b", "8c", "8d", "8e", "8f",
            "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9a", "9b", "9c", "9d", "9e", "9f",
            "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "aa", "ab", "ac", "ad", "ae", "af",
            "b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8", "b9", "ba", "bb", "bc", "bd", "be", "bf",
            "c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9", "ca", "cb", "cc", "cd", "ce", "cf",
            "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7", "d8", "d9", "da", "db", "dc", "dd", "de", "df",
            "e0", "e1", "e2", "e3", "e4", "e5", "e6", "e7", "e8", "e9", "ea", "eb", "ec", "ed", "ee", "ef",
            "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8", "f9", "fa", "fb", "fc", "fd", "fe", "ff",
    };

    public static byte[] toBytesFromHex(String hex) {
        byte rc[] = new byte[hex.length() / 2];
        for (int i = 0; i < rc.length; i++) {
            String h = hex.substring(i * 2, i * 2 + 2);
            int x = Integer.parseInt(h, 16);
            rc[i] = (byte) x;
        }
        return rc;
    }

    public static String toHexFromBytes(byte[] bytes) {
        StringBuffer rc = new StringBuffer(bytes.length * 2);
        for (int i = 0; i < bytes.length; i++) {
            rc.append(HEX_TABLE[0xFF & bytes[i]]);
        }
        return rc.toString();
    }
}

Answer 1

On the shoulders of giants etc., using this extension to split your key string up into pairs of characters:

// From https://stackoverflow.com/a/34454633/325366
extension Collection {
    var pairs: [SubSequence] {
        var startIndex = self.startIndex
        let count = self.count
        let n = count/2 + count % 2
        return (0..<n).map { _ in
            let endIndex = index(startIndex, offsetBy: 2, limitedBy: self.endIndex) ?? self.endIndex
            defer { startIndex = endIndex }
            return self[startIndex..<endIndex]
        }
    }
}

... we can turn your key String into a [UInt8] :

let keyBytes = key.pairs.map { byteStr -> UInt8 in
    var value: UInt32 = 0
    Scanner(string: String(byteStr)).scanHexInt32(&value)
    return UInt8(clamping: value)
}

... and anticipating a desire to print the final hex value out we can write an extension on Array :

extension Array where Element == UInt8 {
    var asHexString: String {
        return self.map { String(format: "%0x", $0) }
                   .joined()
    }
}

... which results in your original code:

let stringArr: Array<UInt8> = Array(string.utf8)
do {
    let authenticator = HMAC(key: keyBytes, variant: .md5)
    let hmac = try authenticator.authenticate(stringArr)

    print("Message HMAC: \(hmac.asHexString)")
} catch { }

... printing out the value you are looking for:

Encrypted string: 7eda9d3c1356402e6fce39af3bc8d195