This specification gives a detailed specification of the 3GPP confidentiality algorithm f8, and the 3GPP integrity
Each of these algorithms is based on the KASUMI algorithm that is specified in TS 35.202
. KASUMI is a block cipher that produces a 64-bit output from a 64-bit input under the control of a 128-bit key.
The confidentiality algorithm f8 is a stream cipher that is used to encrypt/decrypt blocks of data under a confidentiality key CK. The block of data may be between 1 and 20000 bits long. The algorithm uses KASUMI in a form of output feedback mode as a keystream generator.
The integrity algorithm f9 computes a 32-bit MAC (Message Authentication Code) of a given input message using an integrity key IK. The approach adopted uses KASUMI in a form of CBC-MAC mode.