A Digital Signature Scheme for Long-Term Security

In this paper we propose a signature scheme based on two intractable problems, namely the integer factorization problem and the discrete logarithm problem for elliptic curves. It is suitable for applications requiring long-term security and provides a more efficient solution than the existing ones

A new RSA public key encryption scheme with chaotic maps

Public key cryptography has received great attention in the field of information exchange through insecure channels. In this paper, we combine the Dependent-RSA (DRSA) and chaotic maps (CM) to get a new secure cryptosystem, which depends on both integer factorization and chaotic maps discrete logarithm (CMDL). Using this new system, the scammer has to go through two levels of reverse engineering, concurrently, so as to perform the recovery of original text from the cipher-text has been received. Thus, this new system is supposed to be more sophisticated and more secure than other systems. We prove that our new cryptosystem does not increase the overhead in performing the encryption process or the decryption process considering that it requires minimum operations in both. We show that this new cryptosystem is more efficient in terms of performance compared with other encryption systems, which makes it more suitable for nodes with limited computational ability

New Convertible Authenticated Encryption Scheme with Message Linkages

The digital signature provides the signing message with functions like authentication, integration and non-repudiation. However, in some of the applications, the signature has to be verified only by specific recipients of the message and it should be hidden from the public. For achieving this, authenticated encryption systems are used. Authenticated Encryption schemes are highly helpful to send a confidential message over an insecure network path. In order to protect the recipients benefit and for ensuring non-repudiation, we help the receiver to change the signature from encrypted one to an ordinary one. With this we avoid any sort of later disputes. Few years back, Araki et al. has proposed a convertible authenticated scheme for giving a solution to the problem. His scheme enables the recipient to convert the senders signature into an ordinary one. However, the conversion requires the cooperation of the signer. In this thesis, we present a convertible authenticated encryption scheme that can produce the ordinary signature without the cooperation of the signer with a greater ease. Here, we display a validated encryption plan using message linkages used to convey a message. For the collector's advantage, the beneficiary can surely change the encrypted signature into an ordinary signature that which anyone can check. A few attainable assaults shall be examined, and the security investigation will demonstrate that none of the them can effectively break the proposed plan

Solving discrete logarithms on a 170-bit MNT curve by pairing reduction

Pairing based cryptography is in a dangerous position following the breakthroughs on discrete logarithms computations in finite fields of small characteristic. Remaining instances are built over finite fields of large characteristic and their security relies on the fact that the embedding field of the underlying curve is relatively large. How large is debatable. The aim of our work is to sustain the claim that the combination of degree 3 embedding and too small finite fields obviously does not provide enough security. As a computational example, we solve the DLP on a 170-bit MNT curve, by exploiting the pairing embedding to a 508-bit, degree-3 extension of the base field.Comment: to appear in the Lecture Notes in Computer Science (LNCS

Algorithms and cryptographic protocols using elliptic curves

En els darrers anys, la criptografia amb corbes el.líptiques ha adquirit una importància creixent, fins a arribar a formar part en la actualitat de diferents estàndards industrials. Tot i que s'han dissenyat variants amb corbes el.líptiques de criptosistemes clàssics, com el RSA, el seu màxim interès rau en la seva aplicació en criptosistemes basats en el Problema del Logaritme Discret, com els de tipus ElGamal. En aquest cas, els criptosistemes el.líptics garanteixen la mateixa seguretat que els construïts sobre el grup multiplicatiu d'un cos finit primer, però amb longituds de clau molt menor. Mostrarem, doncs, les bones propietats d'aquests criptosistemes, així com els requeriments bàsics per a que una corba sigui criptogràficament útil, estretament relacionat amb la seva cardinalitat. Revisarem alguns mètodes que permetin descartar corbes no criptogràficament útils, així com altres que permetin obtenir corbes bones a partir d'una de donada. Finalment, descriurem algunes aplicacions, com són el seu ús en Targes Intel.ligents i sistemes RFID, per concloure amb alguns avenços recents en aquest camp.The relevance of elliptic curve cryptography has grown in recent years, and today represents a cornerstone in many industrial standards. Although elliptic curve variants of classical cryptosystems such as RSA exist, the full potential of elliptic curve cryptography is displayed in cryptosystems based on the Discrete Logarithm Problem, such as ElGamal. For these, elliptic curve cryptosystems guarantee the same security levels as their finite field analogues, with the additional advantage of using significantly smaller key sizes. In this report we show the positive properties of elliptic curve cryptosystems, and the requirements a curve must meet to be useful in this context, closely related to the number of points. We survey methods to discard cryptographically uninteresting curves as well as methods to obtain other useful curves from a given one. We then describe some real world applications such as Smart Cards and RFID systems and conclude with a snapshot of recent developments in the field

An Analysis of Modern Cryptosystems

Since the ancient Egyptian empire, man has searched for ways to protect information from getting into the wrong hands. Julius Caesar used a simple substitution cipher to protect secrets. During World War II, the Allies and the Axis had codes that they used to protect information. Now that we have computers at our disposal, the methods used to protect data in the past are ineffective. More recently, computer scientists and mathematicians have been working diligently to develop cryptosystems which will provide absolute security in a computing environment. The three major cryptosystems in use today are DES, RSA, and the Knapsack Cryptosystem. These cryptosystems have been reviewed and the positive and negative aspects of each is discussed. A newcomer to the field of cryptology is the Random Spline Cryptosystem which is discussed in detail

A novel group signature scheme without one way hash

The group signatures scheme was introduced by Chaum and van Heijst which allow members of a group to sign messages anonymously on behalf of the whole group. Only a designated Group Manager is able to trace the identify of the group member who issued a valid signature. The group members sign a message with their secret key gsk and produce a signature that cannot be linked to the identities of the signers without the secret key of the manager. The group manager can open the signature to recover the identities of the signers in case of any legal dispute. Group signatures have been widely used in Electronic markets where the sellers are the group members, the buyers are the veriers and the market administrator is the group manager. We aim to propose a group signature scheme that is devoid of any one-way hash function and is based upon the Integer Factorization Problem (IFP). The scheme uses the concept of safe primes to further enhance the security of the scheme. The scheme supports message recovery and hence the overload of sending the message is avoided. The scheme satisfies security properties such as Anonymity (The verier cannot link a signature to the identity of the signer), Traceability (The Group Manager can trace the identity of the signer of any valid signature), Unforgeability (A valid signature cannot be produced without the group secret keys), Exculpability (Neither the GM nor any member can produce a signature on behalf of a group member)