I would like to create a unique key for both account activation and referral purposes, that includes a checksum to help prevent users from easily guessing other users activation or referral keys. Also, in PHP is it possible to create you own session. Generating an MD5 from a unique ID is naive and reduces much of the value of unique IDs, as well as providing significant (attackable) stricture on the MD5 domain. That's a deeply broken thing to do. The correct approach is to use the unique ID on its own; it's already geared for non-collision.
WIndows 10 Pro: VK7JG-NPHTM-C97JM-9MPGT-3V66T. Windows 10 Home Single Language 7HNRX-D7KGG-3K4RQ-4WPJ4-YTDFH. 
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. There are two primary reasons to use session keys:
- 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.
- 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]
Php Generate Unique Id
References[edit]
- ^OpenPGP Message Format http://tools.ietf.org/html/rfc4880