Efficient commerce protocols based on one-time pads

A message authentication code (MAC) is $(t, \epsilon )$ secure if an attacker cannot forge a valid message with probability better than $\epsilon $ after adaptively obtaining $t$ valid messages. For a fixed key space ${\cal K}$ , it is important for an MAC to support a source space ${\cal S}$ as large as possible, because this implies a bandwidth saving in practice. Hence, we study the possible size of ${\cal S}$ in an MAC through $|{\cal S}|$ or equivalently (to our convenience) the ratio $({\log |{\cal S}|}/{|{\cal K}|})$ for a fixed ${\cal K}$ . Our novelty in the methodology is to regard the MAC function of a given source state as a partition mapping for ${\cal K}$ . Under this view, we obtain an upper bound on $|{\cal S}|$ for a $(t, \epsilon )$ -secure MAC. Then, by analyzing a randomized partition of ${\cal K}$ , we prove the existence of an approximately optimal $(t, \epsilon )$ -secure MAC (in the sense of a large $|{\cal S}|$ ). Our ratio $({\log |{\cal S}|}/{|{\cal K}|})$ is much larger than the previous results, where the previous results usually considered only case $t=1$ by proposing a good universal hashing. This method is hard to extend to the case of a general $t$ as a universal hashing relates only two inputs, while the general case needs to relate $t$ inputs. Finally, we construct a selectively $(1, \epsilon )$ -secure MAC, where an attacker fixes two source states in advance with one for his forgery and the other for his inquiry for a valid message. Our ratio $({\log |{\cal S}|}/{|{\cal K}|})$ in this construction is close to the upper bound of its kind and is significantly larger than our existential result above for case $t=1$ .

Whatsapp is a cross-platform messaging application that allows us to exchange messages without SMS fees, because WhatsApp uses the same internet data package for email, web browsing, and more. The WhatsApp application reportedly has improved the security system of applications that are end to end encryption (E2EE). This proves that the WhatsApp manager paid considerable attention to privacy and security issues for its users. In addition, it also implies an important matter where business actors have begun to realize that the application of cryptographic services is part of a very promising business strategy or even determines the present and future consequences. The consequence of implementing E2EE is the description encryption process that takes place at the application layer (OSI layer). Cryptography is a study that studies methods to send messages in secret (that is, encrypted or disguised) so that only the intended recipient of the message can decode and read the message. For this reason, cirptography is one method that can implement E2EE on whatsapp. One Time Pad (OTP) is a type of symmetry algorithm, each key is only used for one message. If the key is random (cannot be reproduced) and only used once, then the algorithm is perfectly safe. The MAC (Message Authentication Code) is an identifier to prove the authenticity of a document obtained by using meaningless messages obtained from processing some of the contents of the document using a private key .

We present a new secret-prefix MAC (Message Authentication Code) based on hash functions. Just like the well-known HMAC algorithm, the new MAC can utilize current hash functions without modifying their Merkle-Damgard implementations. Indeed, the new MAC is almost the same as HMAC except that the second call to the secret key, which is made at the finalization stage, is omitted . In this way we not only increase efficiency over HMAC but also reduce the cost of managing the key, as the new MAC invokes a key only once at the initialization stage, and the rest of the process depends solely on incoming data. We give a rigorous security proof of the new MAC algorithm. Like HMAC, our new MAC is proven to be a secure PRF (Pseudo-Random Function) based on a reasonable assumption about the underlying compression function. In theory our assumption is neither stronger nor weaker than the PRF-type compression-function requirement for the PRF security of HMAC. In practice our assumption looks somewhat similar to the PRF-type requirement for the security of HMAC.

In emerging applications, such as intelligent automotive systems, Internet-of-Things (IoT) and industrial control systems, the use of conventional message authentication codes (MACs) to provide message authentication and integrity is not possible due to the large size of the MAC output. A straightforward yet naive solution to this problem is to employ a truncated MAC which undesirably sacrifices cryptographic strength in exchange for reduced communication overhead. In this paper, we address this problem by proposing a novel approach for message authentication called Cumulative Message Authentication Code (CuMAC), which consists of two distinctive procedures: aggregation and accumulation. In aggregation, a sender generates compact authentication tags from segments of multiple MACs by using a systematic encoding procedure. In accumulation, a receiver accumulates the cryptographic strength by verifying the authentication tags and collecting the underlying MAC segments encoded in them. Embodied with these two procedures, CuMAC enables the receiver to achieve an advantageous trade-off between the cryptographic strength and the latency in processing of the authentication tags. We have carried out comprehensive evaluations of CuMAC in two real-world applications: low-power wide-area network and in-vehicle controller area network. Our evaluation methodology included simulations as well as a prototype implementation of CuMAC on a real car.

Network coding is vulnerable to pollution attacks, which prevent receivers from recovering the source message correctly. Most existing schemes against pollution attacks either bring significant redundancy to the original message or require a high computational complexity to verify received blocks. In this paper, we propose an efficient scheme against pollution attacks based on probabilistic key pre-distribution and homomorphic message authentication codes (MACs). In our scheme, each block is attached with a small number of MACs and each node can use these MACs to verify the integrity of the corresponding block with a high probability. Compared to previous schemes, our scheme still leverages a small number of keys to generate MACs for each block, but more than doubles the detection probability.Meanwhile, our scheme is able to efficiently restrict pollution propagation within a small number of hops. Experimental results show that our scheme is more efficient in verification than existing ones based on public-key cryptography.

Recent parallelizable message authentication codes (MACs) have demonstrated the benefit of tweakable block ciphers (TBCs) for authentication with high security guarantees. With ZMAC, Iwata et al. extended this line of research by showing that TBCs can simultaneously increase the number of message bits that are processed per primitive call. However, ZMAC and previous TBC-based MACs needed more memory than sequential constructions. While this aspect is less an issue on desktop processors, it can be unfavorable on resource-constrained platforms. In contrast, existing sequential MACs limit the number of message bits to the block length of the primitive n or below.This work proposes DoveMAC, a TBC-based PRF that reduces the memory of ZMAC-based MACs to 2n+ 2t+2k bits, where n is the state size, t the tweak length, and k the key length of the underlying primitive. DoveMAC provides (n+min(n+t))/2 bits of security, and processes n+t bits per primitive call. Our construction is the first sequential MAC that combines beyond-birthday-bound security with a rate above n bits per call. By reserving a single tweak bit for domain separation, we derive a single-key variant DoveMAC1k.

Efficiently integrity verification of received data requires Message Authentication Code (MAC) tags. However, while security calls for rather long tags, in many scenarios this contradicts other requirements. Examples are strict delay requirements (e.g., robot or drone control) or resource-scarce settings (e.g., LoRaWAN networks with limited battery capacity). Prior techniques suggested truncation of MAC tags, thus trading off linear performance gain for exponential security loss. To achieve security of full-length MACs with short(er) tags, we introduce Progressive MACs (ProMACs) -- a scheme that uses internal state to gradually increase security upon reception of subsequent messages. We provide a formal framework and propose a provably secure, generic construction called Whips. We evaluate applicability of ProMACs in several realistic scenarios and demonstrate example settings where ProMACs can be used as a drop-in replacement for traditional MACs.

In cognitive radio networks, cooperative spectrum sensing (CSS) is generally adopted for improving spectrum sensing accuracy to increase spectrum utilization and avoid interference with the primary users. However, some malicious secondary users (SUs) may affect the CSS performance by inducing false observation bits for fusion. The message authentication code (MAC) is a promising technique to avoid the damage from the spectrum sensing data falsification (SSDF) attacks. In this paper, as both the more spectrum sensing nodes and the MAC reporting bits result in extra energy consumption, we propose an energy efficiency model to capture the effects of the length of MAC and the number of cooperative SUs under independent and collaborative SSDF attacks, respectively, and analyze the existence of the optimal length of MAC and the optimal number of cooperative SUs that can achieve the maximum value of energy efficiency, respectively. Simulation results are provided to show that the CSS scheme based on MAC can resist SSDF attacks and the accuracy of the theoretical analysis is also validated.

We propose a new message authentication code (MAC) based on a tweakable block cipher (TBC). We prove that the new MAC is a pseudo-random function (PRF) up to $$O(2^n)$$ queries, that is, full PRF-security, where the output length of the TBC is n bits. We note that although Yasuda proposed a full PRF-secure MAC based on a compression function (CF), that does not offer a full PRF-secure TBC-based MAC due to the PRF/PRF switch. Hence our MAC is the first full PRF-secure one based on a TBC.

The protection of data and applications in the cloud is ensured by Cloud Security (CS), whereas bank details are safeguarded from unauthorized access by authentication. But, the existing techniques failed to focus on the data’s sensitivity level, thus leading to inadequate protection of significant information in the cloud. The novelty of this work lies in the design of a sensitivityaware, multi-technique cryptographic framework that integrates ΠS-based Fuzzy (ΠSFuzzy), Stratified-Convenience-centric Biometric Curve Cryptography (SCBCC), and Vigenére-Caesar Cipher-centric Message Authentication Code (VC 2 -MAC) within a secured Smart Contract and IPFS environment to ensure layered data security and precise authentication. The Data Owner (DO) first registers and logs in to upload bank details to the cloud. The texts are further preprocessed. Then, keywords are extracted from the bank details for categorizing the sensitivity levels of data by utilizing ΠSFuzzy. Thereafter, the secured Smart Contract (SC) is created for confidential and restricted data, followed by hashcode generation and Message Authentication Code (MAC) creation. In the meantime, the data is secured and stored in the Interplanetary File System (IPFS). The Cloud User (CU) logs in and sends requests to DO to download the bank details. Finally, the MAC is verified for highly sensitive data within 1099 ms to decline or download the bank details for authorized users. Thus, this work performed superior to the conventional methods. Moreover, the proposed TDGPS-KAnonymity approach achieved a higher PPR of 98.93%, which is 3.48% higher than the existing K-Anonymity technique. The study signified the proposed approach’s superior effectiveness in preserving data privacy while maintaining performance efficiency.

Message authentication codes (MACs) are widely used to protect data integrity and data origin authentication in communications. In this paper, we propose a new block-cipher-based MAC algorithm, CBCR, with provable security for arbitrary-length messages. CBCR adopts rotating operations in the end of cipher- block-chaining structure, and it appends fixed-length prefixes to all messages, which implies flexible usages in practice. For example, these fixed-length prefixes can be filled with some security parameters, message redun- dancies, etc. We also propose CBCR0, a special case of CBCR that sets its prefix to be an all-zero block. Compared with CMAC, a recommended standard by the US National Institute of Standards and Technology (NIST), CBCR0 enjoys all the advantages that CMAC has, but requires less memory; so, in practical appli- cations, CBCR0 behaves as well as CMAC does, and it is even more suitable for environments with limited memory resources, e.g. smart cards.

In this paper, we propose a method to provide message authentication and integrity for a facsimile (fax) document using Message authentication code (MAC) based approach. The proposed method is divided into two parts; sender and receiver. Basically, at the sender side, a MAC value derived from the fax content and a predefined secret key is added to the document before sending it to the receiver via fax. At the receiver side, the modification of fax content can be detected by the use of the agreed MAC and secret key, and the MAC value added on the received fax. The experimental results, from the fax transmission over insecure communication channels, using different types of fax machine, font types and font sizes, demonstrate the promising results.

A Message Authentication Code (MAC), also known as a cryptographic checksum or a keyed hash function, is widely used in practice. In terms of security functionality, MACs share some properties with digital signatures, since they also provide message integrity and message authentication. However, unlike digital signatures, MACs are symmetric-key schemes and they do not provide nonrepudiation. One advantage of MACs is that they are much faster than digital signatures since they are based on either block ciphers or hash functions.

With the development of Internet computing techniques, continuous data streams from remote sites are commonly used in scientific and commercial applications. Correspondingly, there is increasing demand of assuring the integrity and authenticity of received data streams. Existing strategies of assuring data integrity and authenticity mainly use message authentication codes (MAC) generated on data blocks and transfer the MAC to the receiver for authentication through either out of band communication or in band communication. Transferring the MAC via out of band communication inevitably introduces communication overhead and additional complexity to synchronize the out of band communication with the data communication. Transferring the MAC via in band channel can be achieved by either appending the MAC to the original data or embedding the MAC into the original data, which would either incur communication overhead or change the original data. It would be desirable to be able to authenticate the stream data without any communication overhead and changing the original data at the same time. To deal with data packet or block loss, many of existing stream data authentication schemes rely on hash chaining, the current usage of which results in uncertainty in authenticating the subsequent data blocks once the first data packet or block loss is detected. In this paper, we propose a novel application layer authentication strategy called DaTA. This authentication scheme requires no change to the original data and causes no additional communication overhead. In addition, it can continue authenticating the rest of data stream even if some data loss has been detected. Our analysis shows that our authentication scheme is robust against packet loss and network jitter. We have implemented a prototype system to evaluate its performance. Our empirical results show that our proposed scheme is efficient and practical under various network conditions

We consider the problem of constructing anonymous credentials for use in a setting where the issuer of credentials is also the verifier, or more generally where the issuer and verifier have a shared key. In this setting we can use message authentication codes (MACs) instead of public key signatures as the basis for the credential system. To this end, we construct two algebraic MACs in prime-order groups, along with efficient protocols for issuing credentials, asserting possession of a credential, and proving statements about hidden attributes (e.g., the age of the credential owner). We prove the security of the first scheme in the generic group model, and prove the security of the second scheme\dash using a dual-system-based approach\dash under decisional Diffie-Hellman (DDH). Our MACs are of independent interest, as they are the only uf-cmva-secure MACs with efficient proofs of knowledge. Finally, we compare the efficiency of our new systems to two existing constructions of anonymous credentials: U-Prove and Idemix. We show that the performance of the new schemes is competitive with U-Prove (which does not have multi-show unlinkability), and many times faster than Idemix.