What is Logon Encryption for?
The answer is that TLS protects the wire, not the browser. The password exists in plaintext on the client long before it reaches the wire, and it lives there in several uncomfortable places:
• In the DOM and in JavaScript memory, where any browser extension with content-script access can read it.
• In endpoint memory, where infostealer malware scrapes form fields and browser processes.
• In any TLS-terminating middlebox on the path. Corporate SSL inspection proxies decrypt, inspect, and re-encrypt. For the few milliseconds the proxy holds the request, your user's password is sitting in plaintext inside a device you may not fully control, and sometimes inside that device's logs.
Logon Encryption closes exactly this gap. NetScaler delivers an RSA public key to the login page, the browser encrypts the credential fields client-side before the POST leaves, and only the appliance's private key can decrypt them. A TLS-inspecting proxy now sees ciphertext where the password used to be. A malicious extension reading the form sees ciphertext. The password is protected from the moment it is typed until it reaches the box, not just from the moment it hits the network.