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An agreement scheme is presented for the Diffie-Hellman exponentially g/sup xy/ as a keying material via password authentication. The proposed scheme secures a weakly-chosen password and prevents password file compromises.

A password-based method is described which modifies the Diffie-Hellman key agreement protocol to provide user authentication. It is simpler than previously published schemes, prevents the man-in-the-middle attack and requires only two packets to agree on the secret session key. An optional exchange of two more packets allows the key agreement to be verified.

Recently, Wu and Sung reported a one-time digital signature based on any one-way function in their article about password authentication. Owing to its general construction and potential applications, including the development of a one-time password scheme, in-depth security analysis is considered in the Letter. It is shown to suffer from a signature forgery problem.

A remote password authentication scheme based on the Chinese remainder theorem is proposed. The scheme can verify the remote password without verification tables. In the initial phase, the password generation centre generates and assigns a password corresponding to each user. The ideas of smart cards and the identity-based signature scheme introduced by Shamir are employed in this phase. Each user possesses a smart card for later login and authentication. In the login phase, the user submits the identity and password associated with the smart card. In the authentication phase, the system verifies the remotely submitted password to check if the login request is accepted or rejected. A signature scheme and communication timestamps are provided in the authentication phase against the potential attacks of replaying a previously intercepted login request.

This paper evaluates a number of methods for authentication and passwording. It first discusses the role of authentication as a component in an overall approach to information system security. It then classifies the various approaches to authentication into two categories: natural properties and artificial measures. Among the artificial measures, password is most common. The paper provides a quantitative measure for password robustness and 'lasting' power. It discusses encryption possibilities and provides a comparative evaluation of various password methods. The paper concludes by providing some guidelines for evaluating authentication methods.

Our work is motivated by the question of whether or not the password scheme used in UNIX is secure. The following password scheme is a somewhat simplified version of the actual password scheme used in UNIX. We feel that this simplified version captures the essential features of the actual password scheme used in UNM. When a user logs in for the first time he creates a random password and types his user name together with the password into the system. The system creates an encryption of the password using the Data Encryp- tion Standard (DES) and stores this (only the encryption, not the password) together with the user name in a password file. Thereafter, whenever the user logs in and types in his user name and password the system computes the encryption of the password and only allows the user to successfully log in if the encryption matches the entry stored with the user name in the password file.

Despite warnings against it, students persist in using easy-to-guess passwords. This program, intended for use by UNIX system administrators, provides an object lesson. It attacks the one-way-encrypted password file and when it guesses a password, stores an encrypted warning message in the user's area. The user's password is the crypto key. We also demonstrate the vulnerability of a UNIX system to massive password search using high speed computing resources.

In many computer operating systems a user authenticates himself by entering a secret password known solely to himself and the system. The system compares this password with one recorded in a Password Table which is available to only the authentication program. The integrity of the system depends on keeping the table secret. In this paper a password scheme is presented which does not require secrecy in the computer. All aspects of the system, including all relevant code and data bases, may be known by anyone attempting to intrude. The scheme is based on using a function H which the would-be intruder is unable to invert. This function is applied to the user's password and the result compared to a table entry, a match being interpreted as authentication of the user. The intruder may know all about H and have access to the table, but he can penetrate the system only if he can invert H to determine an input that produces a given output. This paper discusses issues surrounding selection of a suitable H . Two different plausible arguments are given that penetration would be exceedingly difficult, and it is then argued that more rigorous results are unlikely. Finally, some human engineering problems relating to the scheme are discussed.

Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing.

Due to the increasing value of information being stored in computers, it is important that unforgeable user authentication policies are implemented. Existing password authentication schemes, threats and counter-measures are described. A solution to eavesdropping problems using public-key cryptography is proposed. A technique to allow long password-phrases that makes an exhaustive search impracticable is presented.

One of the most commonly used two-factor user authentication mechanisms nowadays is based on smart-card and password. A scheme of this type is called a smart-card-based password authentication scheme. The core feature of such a scheme is to enforce two-factor authentication in the sense that the client must have the smart-card and know the password in order to gain access to the server. In this paper, we scrutinize the security requirements of this kind of schemes, and propose a new scheme and a generic construction framework for smart-card-based password authentication. We show that a secure password based key exchange protocol can be efficiently transformed to a smart-card-based password authentication scheme provided that there exist pseudorandom functions and target collision resistant hash functions. Our construction appears to be the first one with provable security. In addition, we show that two recently proposed schemes of this kind are insecure.

Password authentication is one of the most common and elementary applications of encryption techniques, and when these authentication services are embedded into the underlying operating system, their security is usually assured. However, there are an increasing number of systems requiring authentication services which are layered on top of a host operating system. In these cases, the security of the application system is highly dependent on the security of the password file, and, when operating outside the host operating system, compromises of the password file need to be taken seriously. In this paper we propose three different password protection schemes which preserve system security even if the password file is compromised. These schemes are based on the concepts of public-key cryptography: public-key encryption, public-key distribution and quadratic residues. In each scheme the user's password is effectively bound to the user's identification, regardless of the state of the password file, in a time-efficient and simple manner. We discuss the special features, degree of secrecy, advantages and disadvantages for each scheme.

Typical protocols for password-based authentication assume a single server that stores all the information (e.g., the password) necessary to authenticate a user. An inherent limitation of this approach, assuming low-entropy passwords are used, is that the userʼs password is exposed if this server is ever compromised. To address this issue, it has been suggested to share a userʼs password information among multiple servers, and to have these servers cooperate (possibly in a threshold manner) when the user wants to authenticate. We show here a two-server version of the password-only key-exchange protocol of Katz, Ostrovsky, and Yung (the KOY protocol). Our work gives the first secure two-server protocol for the password-only setting (in which the user need remember only a password, and not the serversʼ public keys), and is the first two-server protocol (in any setting) with a proof of security in the standard model. Our work thus fills a gap left by the work of MacKenzie et al. (2006) [31] and Di Raimondo and Gennaro (2006) [16]. As an additional benefit of our work, we show modifications that improve the efficiency of the original KOY protocol.

In this paper, two password authentication schemes, based on triangle and straight line encoding, respectively, are proposed. In our schemes, a one-way function and a strong cryptographic operation such as DES (data encryption standard) are adopted. Besides, in each scheme, the system only needs to store a secret key pair, and each user can select his own password freely. Instead of storing a password verification table inside the computer system, both methods proposed only have to store a corresponding table of identities, which is used by the computer system for validating the submitted passwords. Owing to these two schemes quickly and efficiently responding to any log-in attempt, they are suitable for real-time applications. Furthermore, in each scheme, the system does not need to reconstruct any term of the existing key table when a new user is inserted into the system. Thus, these two schemes are suitable for practical implementation.

In recent years, there has been a growing interest in the cloud computing paradigm thanks to its benefits, such as multi-tenancy, scalability, cost efficiency and its unlimited storage. However, like any new technology, there are still a number of challenges relevant to this paradigm and most notably user authentication. In order to achieve better security than the alphanumerical password, this paper describes a scheme which allows strengthening the authentication process in the cloud environment using the password generator module by means of a combination of different techniques such as multi-factor authentication, One-time password and SHA1.

In 2009, Zheng et al. proposed an efficient password-based group key agreement protocol resistant to the dictionary attacks by adding password-authentication services to a non-authenticated multi-party key agreement protocol proposed by Horng. They claimed that the proposed protocol is very efficient since it only requires constant rounds to agree upon a session key, and each user broadcasts a constant number of messages and only requires four exponentiations. Under the Decisional Diffie-Hellman assumption, they shown the proposed protocol is provably secure in both the ideal-cipher model and the random-oracle model. But in this paper, we show that the protocol Zheng et al. proposed is vulnerable to an active insider attack.

With the rapid growth of the Internet, a lot of electronic patient records (EPRs) have been developed for e-medicine systems. The security and privacy issues of EPRs are important for the patients in order to understand how the hospitals control the use of their personal information, such as name, address, e-mail, medical records, etc. of a particular patient. Recently, Lee et al. proposed a simple group password-based authenticated key agreement protocol for the integrated EPR information system (SGPAKE). However, in this paper, we show that Lee et al.’s protocol is vulnerable to the off-line weak password guessing attack and as a result, their scheme does not provide users’ privacy. To withstand this security weakness found in Lee et al.’s scheme, we aim to propose an effective dynamic group password-based authenticated key exchange scheme for the integrated EPR information system, which retains the original merits of Lee et al.’s scheme. Through the informal and formal security analysis, we show that our scheme provides users’ privacy, perfect forward security and known-key security, and also protects online and offline password guessing attacks. Furthermore, our scheme efficiently supports the dynamic group password-based authenticated key agreement for the integrated EPR information system. In addition, we simulate our scheme for the formal security verification using the widely-accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool and show that our scheme is secure against passive and active attacks.

A method of user password authentication is described which is secure even if an intruder can read the system's data, and can tamper with or eavesdrop on the communication between the user and the system. The method assumes a secure one-way encryption function and can be implemented with a microcomputer in the user's terminal.

We propose and realize a definition of security for password-based key exchange within the framework of universally composable (UC) security, thus providing security guarantees under arbitrary composition with other protocols. In addition, our definition captures some aspects of the problem that were not adequately addressed by most prior notions. For instance, it does not assume any underlying probability distribution on passwords, nor does it assume independence between passwords chosen by different parties. We also formulate a definition of password-based secure channels, and show that such a definition is achievable given password-based key exchange. Our protocol realizing the new definition of password-based key exchange is in the common reference string model and relies on standard number-theoretic assumptions. The components of our protocol can be instantiated to give a relatively efficient solution which is conceivably usable in practice. We also show that it is impossible to satisfy our definition in the “plain” model (e.g., without a common reference string).

Password authentication is the most widely used mechanism for authenticating legal users in multiuser computing systems. Most password authentication schemes keep a password table for verification. However, it is vulnerable to keep such a table. In this paper, we propose a password authentication scheme where the system keeps polynomials instead of a table.

The password which is a more secure and valuable data should be highly protected from eavesdropper. This paper presents how password required for authentication of members of group communication is securely delivered by the source or initiator of the group. The password delivery uses zero knowledge proof and sent to the group member in an encrypted format using cipher block mode encryption. The password delivered is a One Time Password which can be used for certain amount of time in order to ensure a highly secure communication environment among the group.

We propose a simple key agreement protocol(SKA) that provides key establishment with authentication over an insecure channel using only a human memorable password. The SKA is based on Diffie-Hellman scheme and has many of desirable security attributes: it resists off-line dictionary attacks mounted by either passive or active adversaries over network, allowing low-entropy passwords to be used safely. It also offers perfect forward secrecy, which protects past sessions and passwords against future compromise. Besides, it is secure against an adversary who captured a host's password file. Since user passwords are stored in a verifier form, the adversary cannot use it directly to compromise security. The proposed scheme here shows that it is more efficient in computational time and communication overhead over the existing schemes.

The augmented encrypted key exchange (A-EKE) uses a shared secret key for encryption. The A-EKE uses the hash of sender's password as the shared secret key. By using Simmon's attack the sender's password can be broken. If this is accomplished, the attacker is able to know the communicating parties session key used after authentication as well as in the authentication of the sender. Furthermore, using the broken session key and the password, the attacker can impersonate the real sender. To prevent this from happening, we propose a method to keep the session key and sender's password secret even if the attacker can break the shared secret key. This is accomplished by using RSA encryption. In our proposed scheme we use public keys which will be kept by the communicating parties and will be exchanged indirectly, i.e. instead of sending the whole public key the two parties will send the number which determines their public key, along with the shared key.

The original publication is available at www.springerlink.com; International audience; Adaptively-secure key exchange allows the establishment of secure channels even in the presence of an adversary that can corrupt parties adaptively and obtain their internal states. In this paper, we give a formal definition of contributory protocols and define an ideal functionality for password-based group key exchange with explicit authentication and contributiveness in the UC framework. As with previous definitions in the same framework, our definitions do not assume any particular distribution on passwords or independence between passwords of different parties. We also provide the first steps toward realizing this functionality in the above strong adaptive setting by analyzing an efficient existing protocol and showing that it realizes the ideal functionality in the random-oracle and ideal-cipher models based on the CDH assumption.