How to encrypt the cookies generated by LTM?

TCL error: Rule Enterprise_F5_Fix_with_E35-THD_cookie_encrypt HTTP_REQUEST - cant read cookie: no such variable while executing HTTP::cookie value $cookie 



when CLIENT_ACCEPTED {
    Define an AES encryption key. A 128 bit (or larger) key is recommended. 
    You can use a key generator, or create your own using only HEX characters.
   set aes_key "63544a5e7178677b45366b4140"

    Name of the cookie to encrypt/decrypt
   set cookie "app_cookie"

    Log debug messages to /var/log/ltm?  1=yes, 0=no.
   set cookie_encryption_debug 0
}
when HTTP_REQUEST {
    If the error cookie exists with any value, for any requested object, try to decrypt it
   if {[string length [HTTP::cookie value $cookie]]}{

      if {$cookie_encryption_debug}{log local0. \
         "Original error cookie value: [HTTP::cookie value $cookie]"}

       URI decode the value (catching any errors that occur when trying to 
       decode the cookie value and save the output to cookie_uri_decoded)
      if {not ([catch {URI::decode [HTTP::cookie value $cookie]} cookie_uri_decoded])}{

          Log that the cookie was URI decoded
         if {$cookie_encryption_debug}{log local0. "\$cookie_uri_decoded was set successfully"}

          Decrypt the value
         if {not ([catch {AES::decrypt $aes_key $cookie_uri_decoded} cookie_decrypted])}{

             Log the decrypted cookie value
            if {$cookie_encryption_debug}{log local0. "\$cookie_decrypted: $cookie_decrypted"}
         } else {

             URI decoded value couldn't be decrypted.
         }
      } else {
          Cookie value couldn't be URI decoded
      }
   } else {
       Cookie wasn't present in the request
   }
if {[HTTP::uri] ends_with ".asmx?WSDL"}{
set rewrite 1
if { [HTTP::version] eq "1.1" } {
HTTP::version "1.0"
}
} else {
set rewrite 0
}
switch [getfield [string tolower [HTTP::uri]] "/" 2] {
         appe21test {pool test.app_EE_20 }
                  appe21 { pool www.company.com_e20 }
                  appe30 { pool www.company.com_e30 }
                  appe30test { pool www.company.com_e30test }                
                  se08q4 { pool www.company.com_08q4 }  
                  
              }
}
when HTTP_RESPONSE {
    Check if response contains an error cookie with a value
   if {[string length [HTTP::cookie value $cookie]] > 0}{

       Log the original error cookie value from the app
      if {$cookie_encryption_debug}{log local0. \
         "Response from app contained our cookie: [HTTP::cookie value $cookie]"}

       Encrypt the cookie value so the client can't change the value
      HTTP::cookie value $cookie [URI::encode [AES::encrypt $aes_key [HTTP::cookie value $cookie]]]

       Log the encoded and encrypted error cookie value
      if {$cookie_encryption_debug}{log local0. \
        "Encrypted error cookie to: [URI::encode [AES::encrypt $aes_key [HTTP::cookie value $cookie]]]"}
   }
if {$rewrite == 1}{
 collect payload for URI replacement
if {[HTTP::header exists Content-Length]}{
set clength [HTTP::header Content-Length]
} else {
set clength 4294967295
}
if { !($clength == 0) } {
HTTP::collect $clength
}
}
}
when HTTP_RESPONSE_DATA {
set payload [HTTP::payload]
regsub -all {(

 
  
 Aaron