What is a ‘random multicast MAC’? I do not know exactly. Apparently a way to use Version 1 but substituting another MAC rather than the actual MAC of your database server if you are sensitive about disclosing that fact. Like Version 1, but with a random multicast MAC address instead of the real MAC address. Defined by specification as a Version 1 UUID. Commonly used, but avoid if you are sensitive about disclosing the MAC of your database server or the time when this value was generated. The uuid-ossp plugin can generate various versions of UUID.Ĭontains MAC address of current computer + current moment. Uuid_ uuid NOT NULL DEFAULT uuid_generate_v1(), - <= See that command used in the following example table definition. That method call can be made automatically to generate a default value for any newly inserted row. Some people may not want to record the server’s actual MAC address, for example, for security or privacy concerns. Later variations on this theme were developed for alternate kinds of UUIDs. To get the original version of UUID built from the computer’s MAC address plus current date-time plus a small random value, call uuid_generate_v1(). See the extension’s doc to see a list of multiple commands offered for generating various kinds of UUID values. CREATE EXTENSION IF NOT EXISTS "uuid-ossp" A build of this library for Postgres is often bundled with an installation of Postgres such as the graphical installers provided by Enterprise DB or included by cloud providers such as Amazon RDS for PostgreSQL. The extension we want is an open-source library built in C for working with UUIDs, OSSP uuid. See my blog post for more details, or see this page in StackOverflow. To avoid re-installing, add IF NOT EXISTS. To install an extension, call CREATE EXTENSION. In Postgres, a plug-in is known as an extension. While Postgres out-of-the-box supports storing UUID (Universally Unique Identifier) values in their native 128-bit form, generating UUID values requires a plug-in. If you already use the pgcrypto extension, consider the Answer by bpieck. Pkey UUID NOT NULL DEFAULT uuid_generate_v1() , The Postgres server will automatically invoke the function every time a row is inserted. So a randomly generated UUID is no better or worse than a randomly generated session identifier for the same length of random data.Call DEFAULT when defining a column to invoke one of the OSSP uuid functions. If the sessions weren't random or easily guessable, then an attacker could calculate or guess them and hijack established sessions. The server can maintain multiple states since every client uses their own unique session identifier. Simultaneously other clients are doing the same. Notice the data is stored on the server, all the client does is issue requests of whatever kind and tack on the session identifier as a way to maintain state in a stateless system. Every subsequent request from the client carries this identifier so that the server can match the data relevant to that particular client during this particular session. Potentially authentication occurs and some data is stored on the server pertaining that particular session. Server generates a new session id and sends it to client. They have no information or session id at this point. In a typical scenario, client A connects to server B for the first time. They do not encode or encrypt any information, these tokens are used by the server to locate information pertaining the established session. Session identifiers work if they're long random pieces of information. If someone manages to know how the session is encrypted, then he can impersonate all the users: encrypt "1" and set the value as sessionID, encrypts "2" and set the value as sessionID, etc. So it's neither true or false.Ĭonsider that right now the session id is encrypting the auto-increment id (no uuid is used). This entirely relative to a given context. I read that uuid does not bring any security advantages
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