网络安全认证协议形式化分析

1、2022-2-18第二十次全国计算机安全学术交流第二十次全国计算机安全学术交流会会1网络安全认证协议形式化分析肖肖 美美 华华南昌大学信息工程学院南昌大学信息工程学院( (南昌南昌,330029),330029)中国科学院软件研究所计算机科学重点实验室中国科学院软件研究所计算机科学重点实验室( (北京北京,100080),100080)2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会2Organization nIntroductionnRelated WorknFormal System NotationnIntruders Algorithmic Know

2、ledge LogicnVerification Using SPIN/PromelanConclusion 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会3 Introduction nCryptographic protocols are protocols that use cryptography to distribute keys and authenticate principals and data over a network.nFormal methods, a combination of a mathematical or logic

3、al model of a system and its requirements, together with an effective procedure for determining whether a proof that a system satisfies its requirements is correct. Model; Requirement (Specification);Verification. 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会4 Introduction (cont.)In cryptographic protoc

4、ols, it is very crucial to ensure:Messages meant for a principal cannot be read/accessed by others (secrecy);Guarantee genuineness of the sender of the message (authenticity);Integrity;Non-Repudiation (NRO, NRR);Fairness, etc. 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会5Related WorkTechniques of verif

5、ying security properties of the cryptographic protocols can be broadly categorized:nmethods based on belief logics (BAN Logic)n-calculus based models n state machine models (Model Checking) Model checking advantages (compare with theory proving): automatic; counterexample if violation Use LTL (Linea

6、r temporal logic ) to specify properties FDR (Lowe); Mur (Mitchell); Interrogator (Millen); Brutus (Marrero) SPIN (Hollzmann)n theorem prover based methods (NRL, Meadows)n methods based on state machine model and theorem prover (Athena, Dawn)nType checkingnISCAS, LOIS, (in China)2022-2-18第二十次全国计算机安全

7、学术交流会第二十次全国计算机安全学术交流会6Notation(1) Messages a Atom := C | N | k | m Msg := a | m m | mk(2) Contain Relationship () m a m = a m m1 m2 m = m1 m2 m m1 m m2 m m1k m = m1k m m1 Submessage: sub-msgs(m) m Msg | m m 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会7Notation(3) Derivation ( , Dolev-Yao model) m B B m

8、 B m B m B m m (pairing) B m m B m B m (projection) B m B k B mk (encryption) B mk B k-1 B m (decryption) 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会8Notation(4) Properties Lemma 1. B m B B B m Lemma 2. B m B m m B m Lemma 3. B m X m B X （Y: Y sub-msgs(m) : X Y B Y） （b: b B : Y b） （Z, k: Z Msg k Key :

9、 Y = Zk B k-1）Lemma 4. （k, b: k Key b B : k b A k AB k） （z: z sub-msgs(x) : a z A z） (b: b B: a b A a） 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会9Logic of Algorithmic KnowledgeDefinition 1. Primitive propositions P0s for security: p, q P0s := sendi (m) Principal i sent message m recvi (m) Principal i

10、 received message m hasi (m) Principal i has message m 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会10Logic of Algorithmic KnowledgeDefinition 2. An interpreted security system S = (R, R), where R is a system for security protocols, and R is the following interpretation of the primitive propositions in

11、R. R(r, m) (sendi (m) = true iff j such that send (j, m) ri (m) R(r, m) (recvi (m) = true iff recv(m) ri (m) R(r, m) (hasi (m) = true iff m such that m m and recv(m ) ri (m) 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会11Logic of Algorithmic KnowledgeDefinition 3. An interpreted algorithmic security sys

12、tem (R, R, A1, A2, An ), where R is a security system, and R is the interpretation in R, Ai is a knowledge algorithm for principal i. 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会12Algorithm knowledge logic AiDY(hasi(m),l) K = keyof(l) for each recv(m) in l do if submsg(m, m, K) then return “Yes” return

13、 “No”submsg(m, m, K) if m = m then return true if m is m1k and k-1 K then return submsg(m, m1, K) if m is m1 .m2 then return submsg(m, m1, K) submsg(m, m2, K) return false2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会13Cont.getkeys(m, K) if m Key then return m if m is m1k and k-1 K then return getkeys(m1

14、, K) if m is m1 .m2 then return getkeys(m1, K) getkeys(m2, K) return keysof(l) K initkeys(l) loop until no change in K k getkeys(m, K) (when recv(m) l ) return K2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会14Verification Using SPIN/PromelaSPIN is a highly successful and widely used software model-checki

15、ng system based on formal methods from Computer Science. It has made advanced theoretical verification methods applicable to large and highly complex software systems. In April 2002 the tool was awarded the prestigious System Software Award for 2001 by the ACM. SPIN uses a high level language to spe

16、cify systems descriptions, including protocols, called Promela (PROcess MEta LAnguage). 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会15BAN-Yahalom Protocol 1 AB: A, Na 2 BS: B, Nb, A, NaKbs 3 SA: Nb, B, Kab, NaKas , A, Kab, NbKbs 4 AB: A, Kab, NbKbs , NbKab2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会16Atta

17、ck 1 (intruder impersonates Bob to Alice).1 AI(B): A, Na .1 I(B)A: B, Na .2 AI(S): A, Na, B, NaKas .2 I(A)S: A, Na, B, NaKas .3 SI(B): Na, A, Kab, NaKas , B, Kab, NaKbs.3 I(S)A: Ne, B, Kab, NaKas , A, Kab, NaKbs.4 AI(B): A, Kab, NbKbs , NeKab 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会17Attack 2 (intr

18、uder impersonates Alice).1 AB: A, Na.2 BS: B, Nb, A, NaKbs .1 I(A)B: A, (Na, Nb) .2 BI(S): B, Nb, A, Na, NbKas .3 (Omitted).4 I(A)B: A, Na, NbKbs , NbNa 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会18Attack 3.1 AB: A, Na.2 BS: B, Nb, A, NaKbs .1 I(B)A: B, Nb .2 AI(S): A, Na, B, NbKas .2 I(A)S: A, Na, B,

19、 NbKas .3 SI(B): Na, A, Kab, NbKbs , B, Kab, NaKas .3 I(S)A: Nb, B, Kab, NaKas , A, Kab, NbKbs.4 AB: A, Kab, NbKbs , NbKab2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会19Optimization strategies nUsing static analysis and syntactical reordering techniquesnThe two techniques are illustrated using BAN-Yahal

20、om verification model as the benchmark.ndescribe the model as Original version to which static analysis and the syntactical reordering techniques are not applied, nthe static analysis technique is only used as Fixed version(1),nboth the static analysis and the syntactical reordering techniques are u

21、sed as Fixed version(2).2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会20Experimental results show the effectivenessProtocol Model ConfigurationWith type flawsNo type flawsStatesTrans.StatesTrans.Original version15802065549697Fixed version(1)7121690405379Fixed version(2)433512225 2432022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会21Needham-Schroeder Authentication Protocol 2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会22Attack to N-S Protocol (found by SPIN)2022-2-18第二十次全国计算机安全学术交流会第二十次全国计算机安全学术交流会