In information security, message authentication or data origin authentication is a property that a message has not been modified while in transit (data integrity) and that the receiving party can verify the source of the message. Message authentication does not necessarily include the property of non-repudiation.

In the context of an HTTP transaction, basic access authentication is a method for an HTTP user agent (e.g.

<operating system, security> (Or "logon") A unique name for each user of computer services which can be accessed by several persons. Users need to identify themselves for accounting, security, logging, and resource management. Usually a person must also enter a password in order to access a service. Once the user has logged on the operating system will often use a (short) user identifier, e.g. an integer, to refer to them rather than their user name. User names can usually be any short string of alphanumeric characters. Common choices are first name, initials, or some combination of first name, last name, initials and an arbitrary number. User names are often assigned by {system administrators} according to some local policy, or they may be chosen by the users themselves. User names are often also used as mailbox names in electronic mail addresses. (1997-03-16)