An initial block or “footprint” block is the first NXX-X block that a service provider receives in a rate center where the SP has no other assigned resources (FCC 00-104, ¶ 86 and 191).

The first geographic NXX code assigned to a Service Provider for each rate center in which it provides service.

A preliminary statement of the basic security-relevant facts about a system [CESG].
Note: An initial System Security Policy constitutes the basis for the Departmental Security Officer's risk assessment and Security requirement.

In cryptography, a 64-bit binary sector that may be attached to the beginning of a message. [After X9.23]

Initialization is a consumer device setup and initial configuration phase that is either performed at manufacturing time or manually entered by the user. This stage is outside the scope of the ATIS IIF. However, the date elements, such as identity and authentication credentials and their default values, are in scope for the ATIS IIF.

In encryption, a nonsecret binary vector used as the initializing input algorithm for the encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance and to synchronize cryptographic equipment. [After X9.52]

Setting the state of a cryptographic logic prior to key generation, encryption, or other operating mode. [INFOSEC-99]

The mobile switching center (MSC) (switch) that obtains routing information (i.e., LRN). [T1.708-1998]

An entity (e.g., human user or computer based entity) that attempts to access other entities [10181-3].

ADI associated with the initiator [10181-3].