3GPP Confidentiality and Integrity Algorithms UEA2 & UIA2. page 5 of 37
SNOW 3G Algorithm Specification Version 1.1
TABLE OF CONTENTS
1.
Outline of the Normative Part of the Document.................................................................8
2.
Introductory Information ....................................................................................................8
2.1.
Introduction.................................................................................................................8
2.2.
Notation ......................................................................................................................8
3.
Components of SNOW 3G ...............................................................................................10
3.1.
Functions used in different Components of SNOW 3G ...........................................10
3.2.
Linear Feedback Shift Register (LFSR) ...................................................................10
3.3.
Finite State Machine (FSM) .....................................................................................10
3.4.
The Clocking Operations ..........................................................................................11
4.
Operation of SNOW 3G ...................................................................................................12
4.1.
Initialisation ..............................................................................................................12
4.2.
Generation of Keystream ..........................................................................................13
5.
Definition of Tables used in SNOW 3G...........................................................................14
ANNEX 1
Remarks about the mathematical background of some operations of the
SNOW 3G Algorithm...............................................................................................................17
1.1
MULx and MULxPOW............................................................................................17
1.2
The S-Box S
1
used in the FSM .................................................................................17
1.3
The S-Box S
Q
used in the S-Box S2 .........................................................................17
1.4
The S-Box S
2
used in the FSM .................................................................................18
1.5
Interpretation of the 32-bit words contained in the LFSR as elements of
GF(2
32
)..............................................................................................................................18
ANNEX 2
Implementation options for some operations of the SNOW 3G
Algorithm 19
2.1.
The S-Box S
1
used in the FSM .................................................................................19
2.2.
The S-Box S
2
used in the FSM .................................................................................19
2.3.
The functions MUL
α
and DIV
α
used in the LFSR....................................................19
2.4.
Definitions of tables for the FSM .............................................................................20
2.5.
Definitions of tables for the LFSR............................................................................28
ANNEX 3
Figures of the SNOW 3G Algorithm..................................................................30
SNOW 3G Algorithm during key initialisation................................................................30
SNOW 3G Algorithm during keystream-generation........................................................31
ANNEX 4
Simulation Program Listing................................................................................32
4.1.
Header file ................................................................................................................32
4.2.
Code..........................................................................................................................32
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