How can I get SecKeyRef from DER/PEM file

Question

I need to integrate my iPhone app with a system, and they require to encrypt data by a given public key, there are 3 files in 3 different format .xml .der and .pem, I have r

Answer 1

After hours of effort researching online with the help of this post, I finally get it working perfectly. Here is the notes with working Swift code of the most current version. I hope it can help someone!

1. Received a certificate in the base64 encoded string sandwiched between header and tail like this (PEM format):

   -----BEGIN CERTIFICATE-----
   -----END CERTIFICATE-----
   

2. strip out the header and the tail, such as

   // remove the header string  
   let offset = ("-----BEGIN CERTIFICATE-----").characters.count  
   let index = certStr.index(cerStr.startIndex, offsetBy: offset+1)  
   cerStr = cerStr.substring(from: index)  
   
   // remove the tail string 
   let tailWord = "-----END CERTIFICATE-----"   
   if let lowerBound = cerStr.range(of: tailWord)?.lowerBound {  
   cerStr = cerStr.substring(to: lowerBound)  
   }
   

3. decode base64 string to NSData:

   let data = NSData(base64Encoded: cerStr, 
      options:NSData.Base64DecodingOptions.ignoreUnknownCharacters)!  
   

4. Convert it from NSdata format to SecCertificate:

   let cert = SecCertificateCreateWithData(kCFAllocatorDefault, data)
   

5. Now, this cert can be used to compare with the certificate received from the urlSession trust:

   certificateFromUrl = SecTrustGetCertificateAtIndex(...)
   if cert == certificate {
   }