scholarly journals Block Cipher in the Ideal Cipher Model: A Dedicated Permutation Modeled as a Black-Box Public Random Permutation

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1485
Author(s):  
Yasir Nawaz ◽  
Lei Wang
Keyword(s):  
Block Cipher ◽  
Random Permutation ◽  
Secret Key ◽  
Pseudorandom Permutation ◽  
Ideal Cipher ◽  
Xor Operation ◽  
Beyond Birthday Bound ◽  
Symmetric Key Cryptography ◽  
Ideal Cipher Model ◽  
The Ideal

Designing a secure construction has always been a fascinating area for the researchers in the field of symmetric key cryptography. This research aimed to make contributions to the design of secure block cipher in the ideal cipher model whose underlying primitive is a family of n − b i t to n − b i t random permutations indexed by secret key. Our target construction of a secure block ciphers denoted as E [ s ] is built on a simple XOR operation and two block cipher invocations, under the assumptions that the block cipher in use is a pseudorandom permutation. One out of these two block cipher invocations produce a subkey that is derived from the secret key. It has been accepted that at least two block cipher invocations with XOR operations are required to achieve beyond birthday bound security. In this paper, we investigated the E [ s ] instances with the advanced proof technique and efficient block cipher constructions that bypass the birthday-bound up to 2 n provable security was achieved. Our study provided new insights to the block cipher that is beyond birthday bound security.

scholarly journals Security of Symmetric Primitives against Key-Correlated Attacks

2019 ◽  
pp. 193-230
Author(s):  
Aisling Connolly ◽  
Pooya Farshim ◽  
Georg Fuchsbauer
Keyword(s):  
Natural Transformation ◽  
Random Oracle Model ◽  
Random Permutation ◽  
Random Oracle ◽  
Dependent Data ◽  
Authenticated Encryption ◽  
Ideal Cipher ◽  
Permutation Model ◽  
Ideal Cipher Model ◽  
The Ideal

We study the security of symmetric primitives against key-correlated attacks (KCA), whereby an adversary can arbitrarily correlate keys, messages, and ciphertexts. Security against KCA is required whenever a primitive should securely encrypt key-dependent data, even when it is used under related keys. KCA is a strengthening of the previously considered notions of related-key attack (RKA) and key-dependent message (KDM) security. This strengthening is strict, as we show that 2-round Even–Mansour fails to be KCA secure even though it is both RKA and KDM secure. We provide feasibility results in the ideal-cipher model for KCAs and show that 3-round Even–Mansour is KCA secure under key offsets in the random-permutation model. We also give a natural transformation that converts any authenticated encryption scheme to a KCA-secure one in the random-oracle model. Conceptually, our results allow for a unified treatment of RKA and KDM security in idealized models of computation.

scholarly journals CTET+: A Beyond-Birthday-Bound Secure Tweakable Enciphering Scheme Using a Single Pseudorandom Permutation

2021 ◽  
pp. 1-35
Author(s):  
Benoît Cogliati ◽  
Jordan Ethan ◽  
Virginie Lallemand ◽  
Byeonghak Lee ◽  
Jooyoung Lee ◽  
...  
Keyword(s):  
Block Cipher ◽  
Random Permutation ◽  
Pseudorandom Permutation ◽  
Linear Layer ◽  
Non Linear ◽  
Single Block ◽  
Permutation Model ◽  
Beyond Birthday Bound ◽  
Disk Encryption ◽  
Block Sizes

In this work, we propose a construction of 2-round tweakable substitutionpermutation networks using a single secret S-box. This construction is based on non-linear permutation layers using independent round keys, and achieves security beyond the birthday bound in the random permutation model. When instantiated with an n-bit block cipher with ωn-bit keys, the resulting tweakable block cipher, dubbed CTET+, can be viewed as a tweakable enciphering scheme that encrypts ωκ-bit messages for any integer ω ≥ 2 using 5n + κ-bit keys and n-bit tweaks, providing 2n/3-bit security.Compared to the 2-round non-linear SPN analyzed in [CDK+18], we both minimize it by requiring a single permutation, and weaken the requirements on the middle linear layer, allowing better performance. As a result, CTET+ becomes the first tweakable enciphering scheme that provides beyond-birthday-bound security using a single permutation, while its efficiency is still comparable to existing schemes including AES-XTS, EME, XCB and TET. Furthermore, we propose a new tweakable enciphering scheme, dubbed AES6-CTET+, which is an actual instantiation of CTET+ using a reduced round AES block cipher as the underlying secret S-box. Extensivecryptanalysis of this algorithm allows us to claim 127 bits of security.Such tweakable enciphering schemes with huge block sizes become desirable in the context of disk encryption, since processing a whole sector as a single block significantly worsens the granularity for attackers when compared to, for example, AES-XTS, which treats every 16-byte block on the disk independently. Besides, as a huge amount of data is being stored and encrypted at rest under many different keys in clouds, beyond-birthday-bound security will most likely become necessary in the short term.

scholarly journals Duel of the Titans: The Romulus and Remus Families of Lightweight AEAD Algorithms

2020 ◽  
pp. 43-120
Author(s):  
Tetsu Iwata ◽  
Mustafa Khairallah ◽  
Kazuhiko Minematsu ◽  
Thomas Peyrin
Keyword(s):  
Block Cipher ◽  
Computationally Efficient ◽  
Ideal Cipher ◽  
The Standard Model ◽  
Large Memory ◽  
Tweakable Block Cipher ◽  
State Size ◽  
Ideal Cipher Model ◽  
Efficiency Rate ◽  
The Ideal

In this article, we propose two new families of very lightweight and efficient authenticated encryption with associated data (AEAD) modes, Romulus and Remus, that provide security beyond the birthday bound with respect to the block-length n. The former uses a tweakable block cipher (TBC) as internal primitive and can be proven secure in the standard model. The later uses a block cipher (BC) as internal primitive and can be proven secure in the ideal cipher model. Both our modes allow to switch very easily from the nonce-respecting to the nonce-misuse scenario.Previous constructions, such as ΘCB3, are quite computationally efficient, yet needing a large memory for implementation, which makes them unsuitable for platforms where lightweight cryptography should play a key role. Romulus and Remus break this barrier by introducing a new architecture evolved from a BC mode COFB. They achieve the best of what can be possible with TBC – the optimal computational efficiency (rate-1 operation) and the minimum state size of a TBC mode (i.e., (n + t)-bit for n-bit block, t-bit tweak TBC), with almost equivalent provable security as ΘCB3. Actually, our comparisons show that both our designs present superior performances when compared to all other recent lightweight AEAD modes, being BC-based, TBC-based or sponge-based, in the nonce-respecting or nonce-misuse scenario. We eventually describe how to instantiate Romulus and Remus modes using the Skinny lightweight tweakable block cipher proposed at CRYPTO 2016, including the hardware implementation results

scholarly journals New Constructions of MACs from (Tweakable) Block Ciphers

2017 ◽  
pp. 27-58 ◽  
Author(s):  
Benoît Cogliati ◽  
Jooyoung Lee ◽  
Yannick Seurin
Keyword(s):  
Block Cipher ◽  
Block Ciphers ◽  
Message Authentication ◽  
Authentication Codes ◽  
Ideal Cipher ◽  
The Standard Model ◽  
Tweakable Block Cipher ◽  
Ideal Cipher Model ◽  
Provably Secure ◽  
The Ideal

We propose new constructions of Message Authentication Codes (MACs) from tweakable or conventional block ciphers. Our new schemes are either stateless and deterministic, nonce-based, or randomized, and provably secure either in the standard model for tweakable block cipher-based ones, or in the ideal cipher model for block cipher-based ones. All our constructions are very efficient, requiring only one call to the underlying (tweakable) block cipher in addition to universally hashing the message. Moreover, the security bounds we obtain are quite strong: they are beyond the birthday bound, and nonce-based/randomized variants provide graceful security degradation in case of misuse, i.e., the security bound degrades linearly with the maximal number of repetitions of nonces/random values.

scholarly journals Enhanced Content Based Double Encryption Algorithm Using Symmetric Key Cryptography

2017 ◽  
Vol 10 (2) ◽  
pp. 345-351
Author(s):  
Junestarfield Kynshi ◽  
Deepa Jose
Keyword(s):  
Encryption Algorithm ◽  
Secret Key ◽  
Cipher Text ◽  
Xor Operation ◽  
Symmetric Key ◽  
Binary Addition ◽  
Secure Network ◽  
Symmetric Key Cryptography

This paper aims to solve the problems of the existing technique of the content based double encryption algorithm using symmetric key cryptography. Simple binary addition, folding method and logical XOR operation are used to encrypt the content of a plaintext as well as the secret key.This algorithm helps to achieve the secure transfer of data throught the network. It solved the problems of the existing algorithm and provides a better solution. The plaintext are encrypted using the above methods and produce a cipher text. The secret key is encrypted and shared through secure network and without knowing the secret key it is difficult to decipher the text. As per expected, enhanced encryption algorithm gives better result than the existing encryption algorithm.

The Security of Tandem-DM in the Ideal Cipher Model

2016 ◽  
Vol 30 (2) ◽  
pp. 495-518 ◽  
Author(s):  
Jooyoung Lee ◽  
Martijn Stam ◽  
John Steinberger
Keyword(s):  
Ideal Cipher ◽  
Ideal Cipher Model ◽  
The Ideal
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