1、 ETSI EN 302 109 V1.1.1 (2003-10)European Standard (Telecommunications series) Terrestrial Trunked Radio (TETRA);Security;Synchronization mechanism for end-to-end encryptionETSI ETSI EN 302 109 V1.1.1 (2003-10) 2 Reference DEN/TETRA-06117 Keywords air interface, data, DMO, security, speech, TETRA ET
2、SI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice Individual copies of the present document can be
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6、 in all media. European Telecommunications Standards Institute 2003. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand the TIPHON logo are Trade Marks currently being registered by ETSI for the benefit of its Members. 3
7、GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI EN 302 109 V1.1.1 (2003-10) 3 Contents Intellectual Property Rights4 Foreword.4 Introduction 4 1 Scope 5 2 References 5 3 Definitions and abbreviations.5 3.1 Definitions5 3.2 Ab
8、breviations .6 4 End-to-end encryption7 4.1 Introduction 7 4.2 Voice encryption and decryption mechanism.7 4.2.1 Protection against replay.8 4.3 Data encryption mechanism .8 4.4 Exchange of information between encryption units .9 4.4.1 Synchronization of encryption units .9 4.4.2 Encrypted informati
9、on between encryption units .10 4.4.3 Transmission.10 4.4.4 Reception 12 4.4.5 Stolen frame format 12 4.5 Location of security components in the functional architecture.13 4.6 End-to-end Key Management.15 Annex A (informative): Bibliography.16 History 17 ETSI ETSI EN 302 109 V1.1.1 (2003-10) 4 Intel
10、lectual Property Rights IPRs essential or potentially essential to the present document 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 Righ
11、ts (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 server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the ETSI IPR Policy, no investigation, including IP
12、R searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This European Standard (Telecommunications
13、series) has been produced by ETSI Project Terrestrial Trunked Radio (TETRA). National transposition dates Date of adoption of this EN: 3 October 2003 Date of latest announcement of this EN (doa): 31 January 2004 Date of latest publication of new National Standard or endorsement of this EN (dop/e): 3
14、1 July 2004 Date of withdrawal of any conflicting National Standard (dow): 31 July 2004 Introduction The present document replaces the end-to-end encryption clause in each of EN 300 392-7 and ETS 300 396-6. ETSI ETSI EN 302 109 V1.1.1 (2003-10) 5 1 Scope The present document defines the Terrestrial
15、Trunked Radio system (TETRA) synchronization operation for end-to-end encryption algorithms that employ streaming ciphers for voice. The method defined applies equally to Direct Mode Operation (as defined in EN 300 396 (see bibliography) and to Trunked Mode Operation (as defined in EN 300 392 (see b
16、ibliography). 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific refer
17、ence, subsequent revisions do not apply. For a non-specific reference, the latest version applies. Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. 1 ETSI EN 300 392-2: “Terrestrial Trunked Radio (TETRA); Vo
18、ice plus Data (V+D); Part 2: Air Interface (AI)“. 2 ISO 7498-2: “Information processing systems - Open Systems Interconnection - Basic Reference Model - Part 2: Security Architecture“. 3 ETSI ETS 300 395-1: “Terrestrial Trunked Radio (TETRA); Speech codec for full-rate traffic channel; Part 1: Gener
19、al description of speech functions“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: cipher key: value that is used to determine the transformation of plain text to cipher text in a cryptographic algorithm cipher te
20、xt: data produced through the use of encipherment NOTE: The semantic content of the resulting data is not available (ISO 7498-2 2). decipherment: reversal of a corresponding reversible encipherment (ISO 7498-2 2) encipherment: cryptographic transformation of data to produce cipher text (ISO 7498-2 2
21、) encryption state: encryption on or off end-to-end encryption: encryption within or at the source end system, with the corresponding decryption occurring only within or at the destination end system flywheel: mechanism to keep the KSG in the receiving terminal synchronized with the Key Stream Gener
22、ator (KSG) in the transmitting terminal in case synchronization data is not received correctly Initialization Value (IV): sequence of symbols that initializes the KSG inside the encryption unit key stream: pseudo random stream of symbols that is generated by a KSG for encipherment and decipherment E
23、TSI ETSI EN 302 109 V1.1.1 (2003-10) 6 Key Stream Generator (KSG): cryptographic algorithm which produces a stream of binary digits which can be used for encipherment and decipherment NOTE: The initial state of the KSG is determined by the initialization value. Key Stream Segment (KSS): key stream o
24、f arbitrary length plain text: unencrypted source data NOTE: The semantic content is available. proprietary algorithm: algorithm which is the intellectual property of a legal entity synchronization value: sequence of symbols that is transmitted to the receiving terminal to synchronize the KSG in the
25、 receiving terminal with the KSG in the transmitting terminal synchronous stream cipher: encryption method in which a cipher text symbol completely represents the corresponding plain text symbol NOTE: The encryption is based on a key stream that is independent of the cipher text. In order to synchro
26、nize the KSGs in the transmitting and the receiving terminal synchronization data is transmitted separately. time stamp: sequence of symbols that represents the time of day 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: AI Air Interface CK Cipher Key C
27、-plane Control-planeCT Cipher Text DMD-SAP Direct Mode D Service Access Point DMO Direct Mode Operation EKSG End-to-end Key Stream Generator EKSS End-to-end Key Stream Segment F Function HSC Half-Slot Condition HSI Half-Slot Importance HSN Half-Slot Number HSS Half-Slot StolenHSSE Half-Slot Stolen b
28、y Encryption unit IV Initialization Value KSG Key Stream Generator KSS Key Stream Segment L1 Layer 1 L2 Layer 2 L3 Layer 3 MAC Medium Access Control MS Mobile Station PT Plain TextSAP Service Access Point SHSI Stolen Half-Slot Identifier STCH Stolen Channel SV Synchronization Value T/DMA-SAP Trunked
29、 or Direct Mode A Service Access Point T/DMC-SAP Trunked or Direct Mode C Service Access Point T/DMD-SAP Trunked or Direct Mode D Service Access Point TMD-SAP Trunked Mode D Service Access Point Tx Transmit U-plane User-planeV+D Voice + Data ETSI ETSI EN 302 109 V1.1.1 (2003-10) 7 4 End-to-end encry
30、ption 4.1 Introduction End-to-end encryption algorithms and key management are outside the scope of the present document. This clause describes a standard mechanism for synchronization of the encryption system that may be employed when using a synchronous stream cipher. The mechanism also permits tr
31、ansmission of encryption related and other signalling information. The mechanism shall apply only to U-plane traffic and U-plane signalling. The method described uses the Stealing Channel, STCH, for synchronization during transmission (see EN 300 392-2 1, clause 23.8.4). NOTE: This mechanism does no
32、t apply for self-synchronizing ciphers, or for block ciphers. The following are requirements on the end-to-end encryption mechanism: the same mechanisms shall apply in both directions; the synchronization processes shall be independent in each direction; end-to-end encryption shall be located in the
33、 U-plane (above the MAC resident air-interface encryption); transport of plain text and cipher text shall maintain the timing and ordering of half-slot pairing (half slots shall be restored in the same order and with the same boundary conditions at each end of the link); the encryption mechanisms de
34、scribed in this clause are valid for one call instance. 4.2 Voice encryption and decryption mechanism Figure 1 shows a functional diagram of the voice encryption and decryption mechanism based on the synchronous stream cipher principle. This demonstrates the symmetry of transmitter and receiver with
35、 each side having common encryption units. It is assumed that the encryption unit shall generate a key stream in a similar way to the AI encryption unit. The encryption unit is then termed the End-to-end Key Stream Generator (EKSG). EKSG shall have two inputs, a cipher key and an initialization valu
36、e. The initialization value should be a time variant parameter (e.g. a sequence number or a timestamp) that is used to initialize synchronization of the encryption units. The output of EKSG shall be a key stream segment termed EKSS. Function F1shall combine the Plain Text (PT) bit stream and EKSS re
37、sulting in an encrypted Cipher Text (CT) bit stream. Function F1-1shall be the inverse of F1and shall combine the bit streams CT and EKSS resulting in the decrypted bit stream PT. Function F2shall replace a half slot of CT with a synchronization frame provided by the “sync control“ functional unit.
38、Function F3shall recognize a synchronization frame in the received CT, and shall supply them to “sync detect“ functional unit. ETSI ETSI EN 302 109 V1.1.1 (2003-10) 8 F 1 -1 F 2 F 3 F 1 PT PT CT CT EKSS EKSS EKSG EKSG IV CK IV CK Synch Detect Synch Control End-to-end transport mechanism SV Synchroni
39、zation frame Synchronization frame Figure 1: Functional diagram of voice encryption and decryption mechanisms Associated with the functional mechanism shall be a crypto-control interface that shall allow the following: selection of CK by use of a key selection value; selection of algorithm by use of
40、 an algorithm number; selection of encryption state (on/off). 4.2.1 Protection against replay Protection against replay should be obtained by use of a time variant initialization value or a similarly time variant cipher key. Possible examples for a time variant initialization value are a timestamp o
41、r sequence number. Time variance of the cipher key may be achieved by deriving a key for each encrypted call. The manner in which time variance is achieved is not addressed by the present document. Recording and replaying of an entire call can be prevented by use of additional data. For example a sh
42、ared call-id range, or a shared real time clock, that validates messages may be used. Means of protecting against call replay are outside the scope of the present document. 4.3 Data encryption mechanism Encryption of circuit mode data preferably should be implemented in the application requiring tra
43、nsport of data. However encryption of circuit mode data may also be achieved by using the voice encryption mechanism. Using the voice encryption mechanism can only gain confidentiality. In order to achieve data integrity other precautions should be taken. NOTE: Any frame stealing will result in loss
44、 of some user application data and alternative mechanisms for recovery of the data should be taken. ETSI ETSI EN 302 109 V1.1.1 (2003-10) 9 4.4 Exchange of information between encryption units Two different cases shall be identified by an appropriate MAC header (see clause 4.4.2): synchronization in
45、formation in clear; or encrypted information. The use of exchanged encrypted information between encryption units is out of the scope of the present document. 4.4.1 Synchronization of encryption units Figure 1 shows the processing blocks “synchronization control“ and “synchronization detect“ and the
46、ir associated functions F2and F3that shall provide the means of synchronizing the EKSG. There shall be two synchronization cases to consider: initial synchronization; and re-synchronization. NOTE: Late entry may be considered a special case of re-synchronization. Both cases shall use frame stealing
47、as a means of inserting synchronization data in the traffic path. Occurrence of stealing in the receiver shall be locally reported to the U-plane application at the TMD-SAP in TETRA V+D and at the DMD-SAP in TETRA DMO. In each case the primitive shall be of type UNITDATA. Table 1 shows the DMD-UNITD
48、ATA primitive (for DMO) that shall be used by the frame stealing mechanism to address the MAC (request) and to inform the U-plane (indication). The parameters in the TMD-UNITDATA primitive in TETRA V+D are identical and are not repeated here. Table 1: Parameters used in the DMD-UNITDATA primitive Pa
49、rameter Request Indication Remark Half slot content M M Half Slot Position (HSN) C C 1sthalf slot or 2ndhalf slot Half Slot Importance (HSI) M - May be defined as: No importance, Low, Medium or High Stolen indication (HSS) M M Not Stolen, Stolen by C-plane, or Stolen by U-plane Half Slot Condition (HSC) - M GOOD, BAD, NULL Table 2 shows the parameters of the DMD-REPORT primitive that shall be used for any further communication from MAC to the U-plane. The parameters in the TMD-REPORT primitive in TETRA V+D are identical and are not
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