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TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Specification of the GEA5 and GIA5 encryption algorithms for
General Packet Radio Service (GPRS);
GEA5 and GIA5 algorithm specification
(3GPP TS 55.251 version 15.0.0 Release 15)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
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3GPP TS 55.251 version 15.0.0 Release 15 1 ETSI TS 155 251 V15.0.0 (2018-07)
Reference
RTS/TSGS-0355251vf00
Keywords
GSM,SECURITY
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3GPP TS 55.251 version 15.0.0 Release 15 2 ETSI TS 155 251 V15.0.0 (2018-07)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
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Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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3GPP TS 55.251 version 15.0.0 Release 15 3 ETSI TS 155 251 V15.0.0 (2018-07)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 5
Introduction . 5
1 Scope . 6
2 References . 6
3 Definitions, symbols and abbreviations . 6
3.1 Definitions . 6
3.2 Symbols . 6
3.3 Abbreviations . 6
4 Introductory information . 7
4.1 Introduction . 7
4.2 Notation . 7
4.2.1 Radix . 7
4.2.2 Conventions . 7
4.2.3 Bit/byte ordering . 7
4.3 List of variables . 7
5 Confidentiality algorithm GEA5 . 8
5.1 Introduction . 8
5.2 Inputs and outputs . 8
5.3 Components and architecture . 9
5.4 Initialisation . 9
5.5 Keystream generation . 9
5.6 Output octets . 9
6 Integrity algorithm GIA5. 9
6.1 Introduction . 9
6.2 Inputs and outputs . 9
6.3 Components and architecture . 10
6.3.1 SNOW 3G . 10
6.3.2 MULx . 10
6.3.3 MULxPOW. 10
6.3.4 MUL . 10
6.4 Initialization . 10
6.5 Calculation . 10
Annex A (informative): Mathematical background of some operations of the GIA5 Algorithm . 11
A.1 The function EVAL_S. 11
A.2 The function MUL(V, P, c) . 11
Annex B (informative): Implementation options for some operations of the GIA5 algorithm . 12
B.1 Overview . 12
B.2. Procedure Pre_Mul_P. 12
B.3 Function Mul_P . 12
Annex C (informative): Figures of the GEA5 and GIA5 algorithms . 13
Annex D (informative): Simulation program listing . 14
D.1 GEA5 . 14
ETSI
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3GPP TS 55.251 version 15.0.0 Release 15 4 ETSI TS 155 251 V15.0.0 (2018-07)
D.2 GIA5 . 14
Annex E (informative): Change history . 15
History . 16
ETSI
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3GPP TS 55.251 version 15.0.0 Release 15 5 ETSI TS 155 251 V15.0.0 (2018-07)
Foreword
This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
Introduction
This specification has been prepared by the 3GPP Task Force, and gives a detailed specification of the 3GPP
confidentiality algorithm GEA5 and the 3GPP integrity algorithm GIA5.
This document is the fi
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