Length In Bits Of A Non-Negative Integer X definition in Computer Security terms:
Definition(s): The length, in bits, of the shortest bit string containing the binary representation of x. For example, the length in bits of 5 (i.e., 101) is 3. When x = 0, its length in bits is 1.
Source(s): NIST SP 800-56B Rev. 1
reference: CSRC Glossary