ETSI TS 135 231 V15.1.0 (2019-10)

Universal Mobile Telecommunications System (UMTS); LTE; Specification of the TUAK algorithm set: A second example algorithm set for the 3GPP authentication and key generation functions f1, f1*, f2, f3, f4, f5 and f5*; Document 1: Algorithm specification (3GPP TS 35.231 version 15.1.0 Release 15)

RTS/TSGS-0335231vf10

General Information

• Status: Published
• Publication Date: 30-Oct-2019
• Technical Committee: 3GPP SA 3 - Security
• Current Stage: 12 - Completion
• Completion Date: 31-Oct-2019

Standards Content (Sample)

ETSI TS 135 231 V15.1.0 (2019-10)






TECHNICAL SPECIFICATION
Universal Mobile Telecommunications System (UMTS);
LTE;
Specification of the TUAK algorithm set: A second example
algorithm set for the 3GPP authentication and key generation
functions f1, f1*, f2, f3, f4, f5 and f5*;
Document 1: Algorithm specification
(3GPP TS 35.231 version 15.1.0 Release 15)

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3GPP TS 35.231 version 15.1.0 Release 15 1 ETSI TS 135 231 V15.1.0 (2019-10)



Reference
RTS/TSGS-0335231vf10
Keywords
LTE,SECURITY,UMTS
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3GPP TS 35.231 version 15.1.0 Release 15 2 ETSI TS 135 231 V15.1.0 (2019-10)
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ETSI

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3GPP TS 35.231 version 15.1.0 Release 15 3 ETSI TS 135 231 V15.1.0 (2019-10)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 4
Introduction . 4
1 Scope . 5
2 References . 5
3 Definitions and symbols . 6
3.1 Definitions . 6
3.2 Symbols . 6
4 Preliminary information . 7
4.1 Introduction . 7
4.2 Notation . 7
4.2.1 Radix . 7
4.2.2 Bit-numbering for inputs and outputs . 7
4.2.3 Assignment operations . 7
4.2.4 Void . 8
4.3 Void . 8
5 Inputs and outputs . 8
5.1 Tuak inputs and outputs . 8
5.2 Keccak and its inputs and outputs . 9
5.3 Other inputs and substrings . 10
6 Definition of the example algorithms . 10
6.1 Derivation of TOP . 10
C
6.2 Specification of the function f1 . 11
6.3. Specification of the function f1* . 12
6.4 Specification of the functions f2, f3, f4 and f5 . 12
6.5 Specification of the function f5* . 14
7 Implementation considerations . 14
7.1 TOP computed on or off the UICC? . 14
C
7.2 Further customization . 15
7.3 Resistance to side channel attacks . 15
Annex A (normative): Tuak diagrams . 16
Annex B (informative): TuakApplication Programme Interface ( AP) in ANSI CI . 17
Annex C (normative): Specification of the Keccak permutation used within Tuak . 18
Annex D (informative): Example source code for Tuak (ANSI C) . 20
Annex E (informative): Example source code for Keccak (ANSI C) . 23
Annex F (informative): Change history . 27
History . 28

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3GPP TS 35.231 version 15.1.0 Release 15 4 ETSI TS 135 231 V15.1.0 (2019-10)
Foreword
rd
This Technical Specification has been produced by the 3 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
The present document is one of three, which between them form the entire specification of the example algorithms,
entitled:
- 3GPP TS 35.231: "Specification of the Tuak algorithm set: A second example algorithm set for the 3GPP
authentication and key generation functions f1, f1*, f2, f3, f4, f5 and f5*;
Document 1: Algorithm specification ".
- 3GPP TS 35.232: "Specification of the Tuak algorithm set: A second example algorithm set for the 3GPP
authentication and key generation functions f1, f1*, f2, f3, f4, f5 and f5*;
Document 2: Implementers’ test data".
- 3GPP TS 35.233: "Specification of the Tuak algorithm Set: A second example algorithm set for the 3GPP
authentication and key generation functions f1, f1*, f2, f3, f4, f5 and f5*;
Document 3: Design conformance test data".
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3GPP TS 35.231 version 15.1.0 Release 15 5 ETSI TS 135 231 V15.1.0 (2019-10)
1 Scope
The present document and the other Technical Specifications in the series, TS 35.232 [15] and 35.233 [16] contain an
example set of algorithms which could be used as the authentication and key generation functions f1, f1*, f2, f3, f4, f5
and f5* for 3GPP systems. All seven functions are operator-specifiable rather than being fully standardised and other
algorithms could be envisaged.
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, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TS 33.102: "3G Security; Security Architecture3G Security; Specification of the
MILENAGE algorithm set: An example algorithm set for the 3GPP authentication and key
generation functions f1, f1*, f2, f3, f4, f5 and f5*; Document 2: Algorithm specification.[3] "The
KECCAK Reference", version 3.0, 14 January 2011, G. Bertoni, J. Daemen, M. Peeters, G. van
Aasche, (available at http://keccak.noekeon.org/Keccak-reference-3.0.pdf).
[4] "KECCAK Implementation Overview", version 3.2, 29 May 2012, G. Bertoni, J. Daemen, M.
Peeters, G. van Aasche, R. van Keer (available at http://keccak.noekeon.org/Keccak-
implementation-3.2.pdf).
[5] "SAKURA: a flexible coding for tree hashing", 3 June 2013, G. Bertoni, J. Daemen, M. Peeters,
G. van Aasche, (available at http://keccak.noekeon.org/Sakura.pdf).
[6] "Securing the AES finalists against Power Analysis Attacks", in FSE 2000, Seventh Fast Software
Encryption Workshop, Thomas S. Messerges, ed. Schneier, Springer Verlag, 2000.
[7] "Timing Attacks on Implementations of Diffie-Hellman, RSA, DSS, and Other Systems", P. C.
Kocher, in CRYPTO'96, Lecture Notes in Computer Science #1109, Springer Verlag, 1996.
[8] "Side Channel Cryptanalysis of Product Ciphers", in ESORICS'98, Lecture Notes in Computer
Science #1485, Springer Verlag, 1998, J. Kelsey, B. Schneier, D. Wagner, C. Hall.
[9] "DES and differential power analysis", in CHES'99, Lecture Notes in Computer Science #1717,
Springer Verlag, 1999, L. Goubin, J. Patarin.
[10] "Differential Power Analysis", in CRYPTO'99, Lecture Notes in Computer Science #1666,
Springer Verlag, 1999, P. Kocher, J. Jaffe, B. Jun.
[11] "On Boolean and Arithmetic Masking against Differential Power Analysis", in CHES'00, Lecture
Notes in Computer Science series, Springer Verlag, 2000, L. Goubin, J.-S. Coron.
[12] 3GPP TS 33.401: "3GPP System Architecture Evolution (SAE); Security architecture".
[13] Void
[14] 3GPP TR 21.905: "Vocabulary for 3GPP specifications".
[15] 3GPP TS 35.232: "3G Security; Specification of the Tuak Algorithm Set: a Second example
algorithm set for the 3GPP authentication and key generation functions f1, f1*, f2, f3, f4, f5 and
f5*; Document 2: Implementers’ test data".
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3GPP TS 35.231 version 15.1.0 Release 15 6 ETSI TS 135 231 V15.1.0 (2019-10)
[16] 3GPP TS 35.233: "3G Security; Specification of the Tuak Algorithm Set: a second example
algorithm set for the 3GPP authentication and key generation functions f1, f1*, f2, f3, f4, f5 and
f5*; Document 3: Design conformance test data".

3 Definitions and symbols
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TR 21.905 [14] and the following apply. A
term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [14].
Tuak: The name of this algorithm set is "Tuak". It should be pronounced like "too-ack".
3.2 Symbols
= The assignment operator
⊕ The bitwise exclusive-OR operation
|| The concatenation of the two operands
th
X[i] The i bit of the variable X. (X = X[0] || X[1] || X[2] || …. )
Π the permutation Keccak-f[1600] (See clause 5.2 and annex C)

The following represent variables used in the algorithm:

AK a 48-bit anonymity key that is the output of either of the functions f5 and f5*
AMF a 16-bit authentication management field that is an input to the functions f1 and f1*
CK a 128-bit or 256-bit confidentiality key that is the output of the function f3
IK a 128-bit or 256-bit integrity key that is the output of the function f4
IN a 1600-bit value that is used as the input to the permutation Π when computing the functions f1,
f1*, f2, f3, f4, f5 and f5*
INSTANCE an 8-bit value that is used to specify different modes of operation and different parameter lengths
within the algorithm set
K a 128-bit or 256-bit subscriber key that is an input to the functions f1, f1*, f2, f3, f4, f5 and f5*
MAC-A a 64-bit, 128-bit or 256-bit network authentication code that is the output of the function f1
MAC-S a 64-bit, 128-bit or 256-bit resynchronization authentication code that is the output of the function
f1*
OP Operator Variant Algorithm Configuration Field (used in MILENAGE)
OUT a 1600-bit value that is taken as the output of the permutation Π when computing the functions f1,
f1*, f2, f3, f4, f5 and f5*
RAND a 128-bit random challenge that is an input to the functions f1, f1*, f2, f3, f4, f5 and f5*
RES a 32-bit, 64-bit, 128-bit or 256-bit signed response that is the output of the function f2
SQN a 48-bit sequence number that is an input to either of the functions f1 and f1*. (For f1* this input
is more precisely called SQN .) See informative Annex C of [1] for methods of encoding
MS
sequence numbers
SQN (See SQN)
MS
TOP a 256-bit Operator Variant Algorithm Configuration Field that is a component of the functions f1,
f1*, f2, f3, f4, f5 and f5*
TOP a 256-bit value derived from TOP and K and used within the computation of the functions
C

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4 Preliminary information
4.1 Introduction
Within the security architecture of the 3GPP system there are seven security functions related to authentication and key
agreement: f1, f1*, f2, f3, f4, f5 and f5*. The operation of these functions falls within the domain of one operator, and
the functions are therefore to be specified by each operator rather than being fully standardized. The algorithms
specified in the present document are examples that may be used by an operator who does not wish to design his own.
The algorithm specified is called Tuak (pronounced "too-ack").
It is not mandatory that the particular algorithms specified in the present document are used.
The inputs and outputs of all seven algorithms are defined in clause 4.4.
4.2 Notation
4.2.1 Radix
The prefix 0x is used to indicate hexadecimal numbers.
4.2.2 Bit-numbering for inputs and outputs
3GPP TS 33.102 [1] includes the following convention. (There is similar text in the specification of MILENAGE, as
defined in 3GPP TS 35.206 [2]):
All data variables in the present document are presented with the most significant substring on the left hand side and the
least significant substring on the right hand side. A substring may be a bit, byte or other arbitrary length bit string.
Where a variable is broken down into a number of substrings, the left-most (most significant) substring is numbered 0,
the next most significant is numbered 1, and so on through to the least significant.
So, for example, RAND[0] is the most-significant bit of RAND and RAND[127] is the least significant bit of RAND.
This convention applies to all inputs and outputs to Tuak, as listed in tables 1 to 9 below.
However, internally to the Tuak specification variables are simply treated as indexed bit strings, without a specific
indication of bit, byte or word order.
4.2.3 Assignment operations
The assignment operator '='is used in many programming languages. Thus:
=
It means that assumes the value that had before the assignment took place. For instance,
x = x + y + 3
means:
(new value of x) becomes (old value of x) + (old value of y) + 3.

Also
=
for lists of variables and expressions, then the left-most variable assumes the value the left-most expression had before
the assignment took place, the next left-most variable assumes the value the next left-most expression had before the
assignment took place, and so on.
For instance,
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3GPP TS 35.231 version 15.1.0 Release 15 8 ETSI TS 135 231 V15.1.0 (2019-10)
x[0].x[2] = 3, 4, 5
means
(new value of x[0]) becomes 3,
(new value of x[1]) becomes 4,
(new value of x[2]) becomes 5.
Whereas:
x[0].x[2] = y[2].y[0]
means
(new value of x[0]) becomes (old value of y[2]),
(new value of x[1]) becomes (old value of y[1]),
(new value of x[2]) becomes (old value of y[0]).
4.2.4 Void
4.3 Void
5 Inputs and outputs
5.1 Tuak inputs and outputs
The inputs to Tuak are given in tables 1 and 2, the outputs in tables 3 to 9 below.
There are a few differences from the inputs and outputs to MILENAGE [2].
We allow tThe key K may be 128 bits or 256 bits. MAC-A and MAC-S may be 64, 128 or 256 bits. RES may be 32, 64,
128 or 256 bits. CK and IK may be 128 or 256 bits. Existing 3GPP specifications (see [1] and [12]) do not support all
these possibilities, but they are included in Tuak for future flexibility in case future releases of these specifications may
want to support them.
NOTE 1: The 3G security architecture specification [1] calls the output of the f1 function 'MAC' while the present
document and [2] call it 'MAC-A'.
Any sizes for the parameters K, MAC-A, MAC-S, RES, CK and IK mentioned in the present document shall not be
supported nor used in entities defined in 3GPP specifications until these specifications explicitly allow their use.
In any particular implementation, the parameters shall have a fixed length, chosen in advance. For example an operator
may fix K at length 256 bits, RES at length 64 bits, CK and IK at length 128 bits. As the lengths do not vary with input,
they are not specified as formal input parameters.
Table 1: Inputs to f1 and f1*
Parameter Size (bits) Comment
K 128 or 256 Subscriber key K[0]…K[127] or K[0]…K[255]
RAND 128 Random challenge RAND[0]…RAND[127]
SQN 48 Sequence number SQN[0]…SQN[47] (for f1* this input is more
precisely called SQNMS)
AMF 16 Authentication management field AMF[0]…AMF[15]

Table 2: Inputs to f2, f3, f4, f5 and f5*
Parameter Size (bits) Comment
K 128 or 256 Subscriber key K[0]…K[127] or K[0]…K[255]
RAND 128 Random challenge RAND[0]…RAND[127]

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3GPP TS 35.231 version 15.1.0 Release 15 9 ETSI TS 135 231 V15.1.0 (2019-10)
Table 3: f1 output
Parameter Size (bits) Comment
MAC-A 64, 128 or Network authentication code MAC-A[0]…MAC-A[63] or MAC-
256 A[0]…MAC-A[127] or MAC-A[0]…MAC-A[255]

Table 4: f1* output
Parameter Size (bits) Comment
MAC-S 64, 128 or Resynch authentication code MAC-S[0]…MAC-S[63] or MAC-
256 S[0]…MAC-S[127] or MAC-S[0]…MAC-S[255]

Table 5: f2 output
Parameter Size (bits) Comment
RES 32, 64, 128 Response RES[0]…RES[31] or RES[0]…RES[63] or
or 256 RES[0]…RES[127] or RES[0]…RES[255]

Table 6: f3 output
Parameter Size (bits) Comment
CK 128 or 256 Confidentiality key CK[0]…CK[127] or CK[0]…CK[255]

Table 7: f4 output
Parameter Size (bits) Comment
IK 128 or 256 Integrity key IK[0]…IK[127] or IK[0]…IK[255]

Table 8: f5 output
Parameter Size (bits) Comment
AK 48 Anonymity key AK[0]…AK[47]

Table 9: f5* output
Parameter Size (bits) Comment
AK 48 Resynch anonymity key AK[0]…AK[47]

NOTE 2: Both f5 and f5* outputs are called AK according to [1]. In practice only one of them at a time will be
calculated in any given call to the authentication and key agreement algorithms.
5.2 Keccak and its inputs and outputs
This clause refers to the Keccak reference specification [3]. Use is made of the permutation Keccak-f[1600], which is
abbreviated to Π, and defined formally in Annex C.
We use Strings IN[0] . IN[1599] and OUT[0] . OUT[1599] are used to represent the input and output of Π. As in [3],
these are treated as simple bit strings. However, to support efficient implementations of Keccak (see [4]), inputs are
mapped to IN and outputs are extracted from OUT in such a way that bits of input and output should not need to be
reversed within bytes for such implementations.
The Keccak specification includes the concept of a security parameter which the designers call "capacity". Based on the
designers' recommendations, a formal capacity of 512 bits is used: all input strings to the Keccak permutation shall be
padded to 1088 bits, and then have 512 zero bits appended. The padding used to extend the input string to 1088 bits is
the "1 0* 1" padding defined in [3], immediately preceded by "1 1 1 1" for consistency with Sakura coding and domain
separation (see e.g. " SAKURA: a flexible coding for tree hashing" [5], start of section 6 for the Sakura coding, and
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3GPP TS 35.231 version 15.1.0 Release 15 10 ETSI TS 135 231 V15.1.0 (2019-10)
Table 4 for the domain separation coding). Note that our input strings before padding are always shorter than 832 bits,
with the remaining bits of IN always the same in all modes, and output is only ever extracted from the first 832 bits of
OUT – so in practice the effective capacity of the construction is at least 1600 - 832 = 768 bits.
5.3 Other inputs and substrings
MILENAGE uses a 128-bit value OP, and derives a 128-bit value OP . OP is an Operator Variant Algorithm
C
Configuration Field.
For Tuak a 256-bit Operator Variant Algorithm Configuration Field is specified, TOP; and a derived 256-bit value
TOPC.
The following internal variables are defined in the algorithm definition:
- A 56-bit string ALGONAME[0] . ALGONAME[55], with an arbitrary fixed value. This is specified as the
ASCII representation of the string "TUAK1.0": to be explicit, ALGONAME[0] . ALGONAME[55] =
0,1,0,1,0,1,0,0, 0,1,0,1,0,1,0,1, 0,1,0,0,0,0,0,1, 0,1,0,0,1,0,1,1, 0,0,1,1,0,0,0,1, 0,0,1,0,1,1,1,0, 0,0,1,1,0,0,0,0
- An 8-bit string INSTANCE[0] . INSTANCE[7] which will be given different values for different algorithms
within the set.
The internal variable INSTANCE is coded using the following schema (sections 6 gives the exact details) :
INSTANCE[0] . INSTANCE[1]  indicate which function is being implemented
INSTANCE[2]…INSTANCE[4]  indicate the length of the MAC-A/MAC-S or RES output,
or they are all set to zero when deriving TOPC
  INSTANCE[5] . INSTANCE[7] indicate whether the CK/IK/K lengths are 256 bit.
6 Definition of the example algorithms
6.1 Derivation of TOP
C
The INSTANCE variable is constructed as follows:
INSTANCE[0] . INSTANCE[6] = 0,0,0,0,0,0,0
INSTANCE[7] = 0 if the length of K is 128 bits
= 1 if the length of K is 256 bits
The 1600-bit value IN is then constructed as follows:
IN[0] . IN[255] = TOP[255] . TOP[0]
IN[256] . IN[263] = INSTANCE[7] . INSTANCE[0]
IN[264] . IN[319] = ALGONAME[55] . ALGONAME[0]
IN[i] = 0 for 320 ≤ i ≤ 511
IN[512] . IN[767] = K[255] . K [0] if the length of K is 256 bits
IN[512] . IN[639] = K[127] . K [0] if the length of K is 128 bits
IN[i] = 0 for 640 ≤ i ≤ 767  if the length of K is 128 bits
IN[i] = 1 for 768 ≤ i ≤ 772
IN[i] = 0 for 773 ≤ i ≤ 1086
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IN[1087] = 1
IN[i] = 0 for 1088 ≤ i ≤ 1599
Then apply the permutation:
OUT = Π(IN)
And extract TOPC as follows:
TOP [0] . TOP [255] = OUT[255] . OUT[0]
C C
6.2 Specification of the function f1
The internal INSTANCE variable is constructed as follows:
INSTANCE[0] . INSTANCE[1] = 0,0
INSTANCE[2] . INSTANCE[4] = 0,0,1  if the MAC-A length is 64 bits
= 0,1,0 if the MAC-A length is 128 bits
     = 1,0,0 if the MAC-A length is 256 bits
INSTANCE[5] . INSTANCE[6] = 0,0
INSTANCE[7] = 0 if the length of K is 128 bits
  = 1 if the length of K is 256 bits
The 1600-bit value IN is then constructed as follows:
IN[0] . IN[255] = TOP [255] . TOP [0]
C C
IN[256] . IN[263] = INSTANCE[7] . INSTANCE[0]
IN[264] . IN[319] = ALGONAME[55] . ALGONAME[0]
IN[320] . IN[447] = RAND[127] . RAND[0]
IN[448] . IN[463]
...