Encrypting url param make too long URL

[eluser]Gilles_T[/eluser]
Hello,

I wrote a function to encode and decode a set of parameters which turned out to be indispensable.
Encoded via : base64_encode(json_encode( all my parameters ))
Decoded via : json_decode(base64_decode( ))

Life was fine. I tried today to make is more secured by adding a encrypt() and decrypt, but sunddenly got a

Forbidden

You don't have permission to access ...My URL...

I noticed that the parameter string length inflated from 220 to more than 1.100 characters.

My interpretation is that the browser sees a truncated URL and sends an error message.

Could someone help me in understanding exactly what happens ?

Thank you for assistance

Gilles