Cloudinary signature generation, in Swift-- using the CryptoSwift Cocoapod for SHA1 hash.

gistfile1.txt

    /* Experimenting with creating a signature to make it easier to do the server-side development.
    See https://github.com/cloudinary/cloudinary_java/blob/master/cloudinary-core/src/main/java/com/cloudinary/Cloudinary.java#L129
    and https://support.cloudinary.com/hc/en-us/articles/203817991-How-to-generate-a-Cloudinary-signature-on-my-own-
    */
    
    // The optional timestamp is for testing this method-- this should be a UNIX timestamp with no trailing decimals-- i.e., just an integer number.
    // Don't use "public_id" or "timestamp" as keys in otherParams if you give it.
    func createSignature(publicId: String, apiSecret: String, otherParams: [String: Any]? = nil, timestamp: String? = nil) -> (signature: String, timestamp: String)? {
        // 1) Set up the parameters we're going to use in the signing.
        var params = [String: Any]()
        
        if let otherParams = otherParams {
            for (key, value) in otherParams {
                params[key] = value
            }
        }
        
        params["public_id"] = publicId
        
        // "UNIX" timestamp
        if let timestamp = timestamp {
            params["timestamp"] = timestamp
        } else {
            params["timestamp"] = "\(Int(Date().timeIntervalSince1970))"
        }
        
        // 2) Sort the keys-- Cloudinary relies on the keys being sorted in ascending order before generating the signature.
        let sortedKeys = params.keys.sorted(by: <)
        
        var toSign:String = ""
        
        // 3) Set up the key=value pairs, with intervening "&" between pairs, for signing
        for key in sortedKeys {
            if toSign.length > 0 {
                toSign += "&"
            }
            
            let value = params[key]!
            toSign += "\(key)=\(value)"
        }
        
        // 4) Cloudinary signature generation relies on the secret being appended to this sequence of key value pairs.
        toSign += apiSecret
        
        guard let toSignData = toSign.data(using: .utf8) else {
            Log.error("Failed converting string to data.")
            return nil
        }
        
        // 5) Generate the SHA1 hash. 
        let signedData = toSignData.sha1()
        
        return (signedData.toHexString(), params["timestamp"] as! String)
    }
    
    func testSignatureCreation() {
        /* From: https://support.cloudinary.com/hc/en-us/articles/203817991-How-to-generate-a-Cloudinary-signature-on-my-own-
         
            Sanity check - Signing the following string:
        
            "public_id=sample_image&timestamp=1315060510abcd"
            where `abcd` is the api_secret, should result with the following signature:
            "b4ad47fb4e25c7bf5f92a20089f9db59bc302313"
        */
        let expectedResult = "b4ad47fb4e25c7bf5f92a20089f9db59bc302313"
        guard let (signature, _) = createSignature(publicId: "sample_image", apiSecret: "abcd", timestamp: "1315060510") else {
            XCTFail()
            return
        }

        XCTAssert(expectedResult == signature)
    }