How cookie is encrypted in persistance profile ?

It's not encrypted like that, a little math will do the trick..

Read this

https://support.f5.com/kb/en-us/solutions/public/6000/900/sol6917.html?sr=42074214

Then tinker with this

https://devcentral.f5.com/wiki/iRules.Persistence_Cookie_Logger.ashx

I think you don't understand correctly my problem. I know how F5 is encoding the IP:port (with and without partitions) that's why i would like to encrypt it (because it's widely known and everyone can decode the IP:port from this cookie). The problem is i can't decode the encrypted cookie in iRule with passpharase that is the same as in the Cookie Persistence Profile. Hope you understand

We use this in a couple iRules

set decryptedCookie [HTTP::cookie decrypt $cookieName $passPhrase "192"]

This is how i have understand it from the F5 doc's, but for me the decrypted value is empty, means the decryption was not ok...

That is the second example from my post.

As i understood from your post - this is working for you. Which version of F5 are you running (my is 11.5.0 HF4) ?

@Derek - Ah sorry about that ;)- yeah HTTP::cookie decrypt is working for us in 11.5 - but on a newer hotfix. We're using a similar syntax to Brads example - Maybe post the complete rule?

@iRuleYou - below is:

1 - the persistence cookie definition:

ltm persistence cookie persist_Test {   
app-service none    
cookie-encryption required  
cookie-encryption-passphrase $M$jb$wzkKy+0kkZgRly/uKWOlcQ== 
cookie-name Test    
defaults-from /Common/cookie    
timeout 180 
}

2 - iRule i'm using for testing:

when CLIENT_ACCEPTED {  
    set encryption_passphrase "7618"    
    set cookiename "Test"
}
when HTTP_REQUEST {
    if {[HTTP::cookie exists $cookiename] } {
        set encrypted [HTTP::cookie $cookiename]
        set decrypted [HTTP::cookie decrypt $cookiename $encryption_passphrase "192"]
        if { ($decrypted eq "") } {
            log local0. "Cookie NOT DECRYPTED Properly !!!!"
        }
        log local0. "Cookie: Encrypted -> $encrypted, Decrypted -> $decrypted"
    }
}
when HTTP_RESPONSE {
    set $pcookie "123456"
    HTTP::cookie insert name $cookiename value $pcookie path "/" 
    HTTP::cookie encrypt $cookiename $encryption_passphrase "192"
}

Right now i can decode the cookie properly, but when i'm encrypting my cookie from iRule then i can't decrypt it properly.

Thanks for any hints on it.