A session key is a single-use symmetric key used for encrypting all messages in one communication session.A closely related term is content encryption key (CEK), traffic encryption key (TEK), or multicast key which refers to any key used for encrypting messages, contrary to other uses like encrypting other keys (key encryption key (KEK) or key wrapping key). Returns the unique identifier, as a string: PHP Version: 4+ Changelog: The prefix parameter became optional in PHP 5.0. The limit of 114 characters long for prefix was raised in PHP 4.3.1. PHP random string generator. Here is how I am doing it to get a true unique random key. PHP How to make generate unique id like Instagram Post. Hi All, I want to create a unique session ID for all evry time user use my application and he can view and change the last activity that hi did on the last page whenever he want while using the the application.

A session key is a single-use symmetric key used for encrypting all messages in one communication session. A closely related term is content encryption key (CEK), traffic encryption key (TEK), or multicast key which refers to any key used for encrypting messages, contrary to other uses like encrypting other keys (key encryption key (KEK) or key wrapping key).

Session keys can introduce complications into a system, yet they solve some real problems. Using openssl to generate key. There are two primary reasons to use session keys:

1. Several cryptanalytic attacks become easier the more material encrypted with a specific key is available. By limiting the amount of data processed using a particular key, those attacks are rendered harder to perform.
2. asymmetric encryption is too slow for many purposes, and all secret key algorithms require that the key is securely distributed. By using an asymmetric algorithm to encrypt the secret key for another, faster, symmetric algorithm, it's possible to improve overall performance considerably. This is the process used by PGP and GPG.^[1]

Like all cryptographic keys, session keys must be chosen so that they cannot be predicted by an attacker, usually requiring them to be chosen randomly. Failure to choose session keys (or any key) properly is a major (and too common in actual practice) design flaw in any crypto system.^{[citation needed]}

See also[edit]

References[edit]

1. ^OpenPGP Message Format http://tools.ietf.org/html/rfc4880

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