Pitfalls in public key cryptosystems based on free partially commutative monoids and groups

At INDOCRYPT 2003 Abisha, Thomas, and Subramanian proposed two public key schemes based on word problems in free partially commutative monoids and groups. We show that both proposals are vulnerable to chosen ciphertext attacks, and thus in the present form must be considered as insecure.This work has been partially supported by the German Academic Exchange Service DAAD and the Spanish M.E.C. as part of the BaSe CoAT project within the Acciones Integradas Hispano-Alemanas

Cryptography with right-angled Artin groups

In this paper we propose right-angled Artin groups as a platform for secret sharingschemes based on the efficiency (linear time) of the word problem. Inspired by previous work of Grigoriev-Shpilrain in the context of graphs, we de ne two new problems: SubgroupIsomorphism Problem and Group Homomorphism Problem. Based on them, we also proposetwo new authentication schemes. For right-angled Artin groups, the Group Homomorphismand Graph Homomorphism problems are equivalent, and the later is known to be NP-complete.In the case of the Subgroup Isomorphism problem, we bring some results due to Bridson whoshows there are right-angled Artin groups in which this problem is unsolvable.Professional Staff Congress-City University of New YorkCity Tech FoundationOffice of Naval ResearchEuropean Research CouncilNational Science FoundationMinisterio de Ciencia e Innovació

Cryptography with right-angled Artin groups

In this paper we propose right-angled Artin groups as a platform for secret sharingschemes based on the efficiency (linear time) of the word problem. Inspired by previous work of Grigoriev-Shpilrain in the context of graphs, we de ne two new problems: SubgroupIsomorphism Problem and Group Homomorphism Problem. Based on them, we also proposetwo new authentication schemes. For right-angled Artin groups, the Group Homomorphismand Graph Homomorphism problems are equivalent, and the later is known to be NP-complete.In the case of the Subgroup Isomorphism problem, we bring some results due to Bridson whoshows there are right-angled Artin groups in which this problem is unsolvable.Professional Staff Congress-City University of New YorkCity Tech FoundationOffice of Naval ResearchEuropean Research CouncilNational Science FoundationMinisterio de Ciencia e Innovació

Attacking a public key cryptosystem based on tree replacement

We point out several security flaws in the cryptosystem based on tree replacement systems proposed by Samuel, Thomas, Abisha and Subramanian at INDOCRYPT 2002. Due to the success of (among others) very simple ciphertext-only attacks, we evidence that this system does not, in its present form, offer acceptable security guarantees for cryptographic applications.Work partially supported by projects BFM2001-3239-C03-01 and BFM2001-1284

Secure web services using two-way authentication and three-party key establishment for service delivery

With the advance of web technologies, a large quantity of transactions have been processed through web services. Service Provider needs encryption via public communication channel in order that web services can be delivered to Service Requester. Such encryptions can be realized using secure session keys. Traditional approaches which can enable such transactions are based on peer-to-peer architecture or hierarchical group architecture. The former method resides on two-party communications while the latter resides on hierarchical group communications. In this paper, we will use three-party key establishment to enable secure communications for Service Requester and Service Provider. The proposed protocol supports Service Requester, Service Broker, and Service Provider with a shared secret key established among them. Compared with peer-to-peer architecture and hierarchical group architecture, our method aims at reducing communication and computation overheads

Attacking a Public Key Cryptosystem Based on Tree Replacement

We point out several security flaws in the cryptosystem based on tree replacement systems proposed by Samuel, Thomas, Abisha and Subramanian at INDOCRYPT 2002. Due to the success of (among others) very simple ciphertext-only attacks, we evidence that this system does not, in its present form, offer acceptable security guarantees for cryptographic applications