Conversion from String to binary and then to base64 format

Question

Trying to create a signature by using RFC 2104-compliant HMAC with the SHA256 hash algorithm. I am half-way done but stuck in converting a string to binary and then to base64 format.

Here is the instruction I am following.

Here is the code I made

let stringToSign = "GET\nwebservices.amazon.com\n/onca/xml\nAWSAccessKeyId=AKIAIOSFODNN7EXAMPLE&AssociateTag=mytag-20&ItemId=0679722769&Operation=ItemLookup&ResponseGroup=Images%2CItemAttributes%2COffers%2CReviews&Service=AWSECommerceService&Timestamp=2014-08-18T12%3A00%3A00Z&Version=2013-08-01"

let beforeCoversion = stringToSign.hmac(algorithm: .SHA256, key: "1234567890")
let binary = beforeCoversion.data(using: .utf8, allowLossyConversion: false)
let afterCoversion = binary?.base64EncodedString(options: [.lineLength64Characters])

print(beforeCoversion)
print(afterCoversion!)

Print

8fb6d93342d767d797799aee4ea5a6d8322f0d8554537c313cfa69fa25f1cd07
OGZiNmQ5MzM0MmQ3NjdkNzk3Nzk5YWVlNGVhNWE2ZDgzMjJmMGQ4NTU0NTM3YzMx
M2NmYTY5ZmEyNWYxY2QwNw==

I can see that I get 8fb6d93342d767d797799aee4ea5a6d8322f0d8554537c313cfa69fa25f1cd07 so my conversion is failed in converting a string to binary and then to base64 format. I believe beforeCoversion.data(using: .utf8, allowLossyConversion: false) can be used for converting a string to binary and binary?.base64EncodedString(options: [.lineLength64Characters]) can be used for converting to base64 format. Is that correct? sAny suggestions?

score 0 · Answer 1 · answered Oct 24 '17 at 16:24

Easy way to solve this if you use amazon-api

pod 'AWSAPIGateway'

Then

let dataToSign = stringToSign.data(using: String.Encoding.utf8)
let conversion = AWSSignatureSignerUtility.hmacSign(dataToSign, withKey: "1234567890", usingAlgorithm: UInt32(kCCHmacAlgSHA256))!

Thanks Roozbeh Zabihollahi for the answer in Amazon Product Advertising API Signature in iOS

Conversion from String to binary and then to base64 format

1 Answers1