网络安全认证协议形式化分析.ppt

网络安全认证协议形式化分析,2019/4/16,第二十次全国计算机安全学术交流会,2,Organization,Introduction Related Work Formal System Notation Intruders Algorithmic Knowledge Logic Verification Using SPIN/Promela Conclusion,2019/4/16,第二十次全国计算机安全学术交流会,3,Introduction,Cryptographic protocols are protocols that use cryptography to distribute keys and authenticate principals and data over a network. Formal methods, a combination of a mathematical or logical 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.,2019/4/16,第二十次全国计算机安全学术交流会,4,Introduction (cont.),In cryptographic protocols, 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.,2019/4/16,第二十次全国计算机安全学术交流会,5,Related Work,Techniques of verifying security properties of the cryptographic protocols can be broadly categorized: methods based on belief logics (BAN Logic) -calculus based models state machine models (Model Checking) Model checking advantages (compare with theory proving): automatic; counterexample if violation Use LTL (Linear temporal logic ) to specify properties FDR (Lowe); Mur (Mitchell); Interrogator (Millen); Brutus (Marrero) SPIN (Hollzmann) theorem prover based methods (NRL, Meadows) methods based on state machine model and theorem prover (Athena, Dawn) Type checking ISCAS, LOIS, (in China),2019/4/16,第二十次全国计算机安全学术交流会,6,Notation,(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 ,2019/4/16,第二十次全国计算机安全学术交流会,7,Notation,(3) Derivation (, Dolev-Yao model) m B B m 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),2019/4/16,第二十次全国计算机安全学术交流会,8,Notation,(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 : 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）,2019/4/16,第二十次全国计算机安全学术交流会,9,Logic of Algorithmic Knowledge,Definition 1. Primitive propositions P0s for security: p, q P0s := sendi (m) Principal i sent message m recvi (m) Principal i received message m hasi (m) Principal i has message m,2019/4/16,第二十次全国计算机安全学术交流会,10,Logic of Algorithmic Knowledge,Definition 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 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),2019/4/16,第二十次全国计算机安全学术交流会,11,Logic of Algorithmic Knowledge,Definition 3. An interpreted algorithmic security system (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.,2019/4/16,第二十次全国计算机安全学术交流会,12,Algorithm 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 “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 false,2019/4/16,第二十次全国计算机安全学术交流会,13,Cont.,getkeys(m, K) if m Key then return m if m is m1k and k-1 K then return getkeys(m1, 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 K,2019/4/16,第二十次全国计算机安全学术交流会,14,Verification Using SPIN/Promela,SPIN is a highly successful and widely used software model-checking 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 specify systems descriptions, including protocols, called Promela (PROcess MEta LAnguage).,2019/4/16,第二十次全国计算机安全学术交流会,15,BAN-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 , NbKab,2019/4/16,第二十次全国计算机安全学术交流会,16,Attack 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,2019/4/16,第二十次全国计算机安全学术交流会,17,Attack 2 (intruder 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,2019/4/16,第二十次全国计算机安全学术交流会,18,Attack 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, 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 , NbKab,2019/4/16,第二十次全国计算机安全学术交流会,19,Optimization strategies,Using static analysis and syntactical reordering techniques The two techniques are illustrated using BAN-Yahalom verification model as the benchmark. describe the model as Original version to which static analysis and the syntactical reordering techniques are not applied, the static analysis technique is only used as Fixed version(1), both the static analysis and the syntactical reordering techniques are used as Fixed version(2).,2019/4/16,第二十次全国计算机安全学术交流会,20,Experimental results show the effectiveness,2019/4/16,第二十次全国计算机安全学术交流会,21,Needham-Schroeder Authentication Protocol,2019/4/16,第二十次全国计算机安全学术交流会,22,Attack to N-S Protocol (found by SPIN),2019/4/16,第二十次全国计算机安全学术交流会,23,Conclusion,based on a logic of knowledge a