Security Enhancement of the Vortex Family of Hash Functions

Vortex is a new family of one-way hash functions which has been submitted to the NIST SHA-3 competition. Its design is based on using the Rijndael block cipher round as a building block, and using a multiplication-based merging function to support fast mixing in a small number of steps. Vortex is designed to be a fast hash function, when running on a processor that has AES acceleration and has a proven collision resistance [2]. Several attacks on Vortex have been recently published [3, 4, 5, 6] exploiting some structural properties of its design, as presented in the version submitted to the SHA-3 competition. These are mainly ¯rst and second preimage attacks with time complexity below the ideal, as well as attempts to distinguish the Vortex output from random. In this paper we study the root-cause of the attacks and propose few amendments to the Vortex structure, which eliminate the attacks without a®ecting its collision resistance and performance

Vortex: A New Family of One Way Hash Functions based on Rijndael Rounds and Carry-less Multiplication

We present Vortex a new family of one way hash functions that can produce message digests of 224, 256, 384 and 512 bits. The main idea behind the design of these hash functions is that we use well known algorithms that can support very fast diffusion in a small number of steps. We also balance the cryptographic strength that comes from iterating block cipher rounds with SBox substitution and diffusion (like Whirlpool) against the need to have a lightweight implementation with as small number of rounds as possible. We use a variable number of Rijndael rounds with a stronger key schedule. Our goal is not to protect a secret symmetric key but to support perfect mixing of the bits of the input into the hash value. Rijndael rounds are followed by our variant of Galois Field multiplication. This achieves cross-mixing between 128-bit or 256-bit sets. Our hash function uses the Enveloped Merkle-Damgard construction to support properties such as collision resistance, first and second pre-image resistance, pseudorandom oracle preservation and pseudorandom function preservation. We provide analytical results that demonstrate that the number of queries required for finding a collision with probability greater or equal to 0.5 in an ideal block cipher approximation of Vortex 256 is at least 1.18x2^122.55 if the attacker uses randomly selected message words. We also provide experimental results that indicate that the compression function of Vortex is not inferior to that of the SHA family regarding its capability to preserve the pseudorandom oracle property. We list a number of well known attacks and discuss how the Vortex design addresses them. The main strength of the Vortex design is that this hash function can demonstrate an expected performance of 2.2-2.5 cycles per byte in future processors with instruction set support for Rijndael rounds and carry-less multiplication. We provide arguments why we believe this is a trend in the industry. We also discuss how optimized assembly code can be written that demonstrates such performance

Vortex: A new family of one-way hash functions based on AES rounds and carry-less multiplication

Abstract. We present Vortex a new family of one way hash functions that can produce message digests of 256 bits. The main idea behind the design of these hash functions is that we use well known algorithms that can support very fast diffusion in a small number of steps. We also balance the cryptographic strength that comes from iterating block cipher rounds with SBox substitution and diffusion (like Whirlpool) against the need to have a lightweight implementation with as small number of rounds as possible. We use only 3 AES rounds as opposed to 10 since our goal is not to protect a secret symmetric key but to support perfect mixing of the bits of the input into the hash value. Three AES rounds are followed by our variant of Galois Field multiplication. This achieves cross-mixing between 128-bit sets. We present a set of qualitative arguments why we believe Vortex supports collision resistance and first pre-image resistance

Cryptographic Constructions Supporting Implicit Data Integrity

We study a methodology for supporting data integrity called \lq implicit integrity\rq $\>$ and present cryptographic constructions supporting it. Implicit integrity allows for corruption detection without producing, storing or verifying mathematical summaries of the content such as MACs and ICVs, or any other type of message expansion. As with authenticated encryption, the main idea behind this methodology is that, whereas typical user data demonstrate patterns such as repeated bytes or words, decrypted data resulting from corrupted ciphertexts no longer demonstrate such patterns. Thus, by checking the entropy of some decrypted ciphertexts, corruption can be possibly detected. The main contribution of this paper is a notion of security which is associated with implicit integrity, and which is different from the typical requirement that the output of cryptographic systems should be indistinguishable from the output of a random permutation. The notion of security we discuss reflects the fact that it should be computationally difficult for an adversary to corrupt some ciphertext so that the resulting plaintext demonstrates specific patterns. We introduce two kinds of adversaries. First, an input perturbing adversary performs content corruption attacks. Second an oracle replacing adversary performs content replay attacks. We discuss requirements for supporting implicit integrity in these two adversary models, and provide security bounds for a construction called IVP, a three-level confusion diffusion network which can support implicit integrity and is inexpensive to implement

Gimli Encryption in 715.9 psec

We study the encryption latency of the Gimli cipher, which has recently been submitted to NIST’s Lightweight Cryptography competition. We develop two optimized hardware engines for the 24 round Gimli permutation, characterized by a total latency or 3 and 4 cycles, respectively, in a range of frequencies up to 4.5 GHz. Specifically, we utilize Intel’s 10 nm FinFET process to synthesize a critical path of 15 logic levels, supporting a depth-3 Gimli pipeline capable of computing the result of the Gimli permutation in frequencies up to 3.9 GHz. On the same process technology, a depth-4 pipeline employs a critical path of 12 logic levels and can compute the Gimli permutation in frequencies up to 4.5 GHz. Gimli demonstrates a total unrolled data path latency of 715.9 psec. Compared to our AES implementation, our fastest pipelined Gimli engine demonstrates 3.39 times smaller latency. When compared to the latency of the PRINCE lightweight block cipher, the pipelined Gimli latency is 1.7 times smaller. The paper suggests that the Gimli cipher, and our proposed optimized implementations have the potential to provide breakthrough performance for latency critical applications, in domains such as data storage, networking, IoT and gaming

ADAGIO: Interactive Experimentation with Adversarial Attack and Defense for Audio

Adversarial machine learning research has recently demonstrated the feasibility to confuse automatic speech recognition (ASR) models by introducing acoustically imperceptible perturbations to audio samples. To help researchers and practitioners gain better understanding of the impact of such attacks, and to provide them with tools to help them more easily evaluate and craft strong defenses for their models, we present ADAGIO, the first tool designed to allow interactive experimentation with adversarial attacks and defenses on an ASR model in real time, both visually and aurally. ADAGIO incorporates AMR and MP3 audio compression techniques as defenses, which users can interactively apply to attacked audio samples. We show that these techniques, which are based on psychoacoustic principles, effectively eliminate targeted attacks, reducing the attack success rate from 92.5% to 0%. We will demonstrate ADAGIO and invite the audience to try it on the Mozilla Common Voice dataset.Comment: Demo paper; for supplementary video, see https://youtu.be/0W2BKMwSfV

K-Cipher: A Low Latency, Bit Length Parameterizable Cipher

We present the design of a novel low latency, bit length parameterizable cipher, called the ``K-Cipher\u27\u27. K-Cipher is particularly useful to applications that need to support ultra low latency encryption at arbitrary ciphertext lengths. We can think of a range of networking, gaming and computing applications that may require encrypting data at unusual block lengths for many different reasons, such as to make space for other unencrypted state values. Furthermore, in modern applications, encryption is typically required to complete inside stringent time frames in order not to affect performance. K-Cipher has been designed to meet these requirements. In the paper we present the K-Cipher design and specification and discuss its security properties. Our analysis indicates that K-Cipher is secure against both known ciphertext, as well as adaptive chosen plaintext adversaries. Finally, we present synthesis results of 32-bit and 64-bit K-Cipher encrypt datapaths. Our results show that the encrypt datapaths can complete in no more than 767 psec, or 3 clocks in 3.9-4.9 GHz frequencies, and are associated with a maximum area requirement of 1875 um^2

The MAGIC Mode for Simultaneously Supporting Encryption, Message Authentication and Error Correction

We present MAGIC, a mode for authenticated encryption that simultaneously supports encryption, message authentication and error correction, all with the same code. In MAGIC, the same code employed for cryptographic integrity is also the parity used for error correction. To correct errors, MAGIC employs the Galois Hash transformation, which due to its bit linearity can perform corrections in a similar way as other codes do (e.g., Reed Solomon). To provide a cryptographically strong MAC, MAGIC encrypts the output of the Galois Hash using a secret key. To analyze the security of this construction we adapt the definition of the MAC adversary so that it is applicable to systems that combine message authentication with error correction. We demonstrate that MAGIC offers security in the order of O(2 to the N/2) with N being the tag size