Does anyone know how the instanceData property of a Geocortex request is encoded?

The entire request is JSON- key-value pairs, arrays, quoted strings, etc. - but the instanceData value is encoded. It looks similar to Base64 until you look closely and see slashes (/) and plus signs (+) throughout the string. I tried various online Base64 decoders but those I tried have been unable to decode the string.

Here's a very small piece of what I found with Fiddler. The entire request is 2+ MB.

"instanceData":"Rrfqn+xQO2IEFTMoYXBfnZQU9FlQf8fCqfRUvCMjc78zthft4xWTh/sIaKW0ySzVnpbSDAog293K+XX32jR/20bxw51t

I've been working on this, here is what I've figured out so far:

Data is:

  • Gzipped using System.IO.Compression.GZipStream
  • Encrypted using some some .net thing
  • Base64 encoded

I'm not sure how to determine the key/encryption scheme used just yet.

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