Topic
Authenticated encryption
About: Authenticated encryption is a research topic. Over the lifetime, 1328 publications have been published within this topic receiving 25968 citations. The topic is also known as: AEAD & Authenticated Encryption with Associated Data.
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19 Oct 2020
TL;DR: This paper focuses on how to build a secure tweakable block cipher from the Key-Alternating Feistel (KAF) structure, a dedicatedFeistel structure with round functions of the form \(F_i(k_i\oplus x_i)\), where k_i is the secret round key and \(F-i\) is a public random function in the i-th round.
Abstract: Tweakable block cipher as a cryptographic primitive has found wide applications in disk encryption, authenticated encryption mode and message authentication code, etc. One popular approach of designing tweakable block ciphers is to tweak the generic constructions of classic block ciphers. This paper focuses on how to build a secure tweakable block cipher from the Key-Alternating Feistel (KAF) structure, a dedicated Feistel structure with round functions of the form \(F_i(k_i\oplus x_i)\), where \(k_i\) is the secret round key and \(F_i\) is a public random function in the i-th round. We start from the simplest KAF structures that have been published so far, and then incorporate the tweaks to the round key XOR operations by (almost) universal hash functions. Moreover, we limit the number of rounds with the tweak injections for the efficiency concerns of changing the tweak value. Our results are two-fold, depending on the provable security bound: For the birthday-bound security, we present a 4-round minimal construction with two independent round keys, a single round function and two universal hash functions; For the beyond-birthday-bound security, we present a 10-round construction secure up to \(O(\min \{ 2^{2n/3}, \root 4 \of {2^{2n}\epsilon ^{-1}} \})\) adversarial queries, where n is the output size of the round function and \(\epsilon \) is the upper bound of the collision probability of the universal hash functions. Our security proofs exploit the hybrid argument combined with the H-coefficient technique.
4 citations
01 Jan 2002
TL;DR: The conclusion is that CCM provides a level of privacy and authenticity that is in line with other proposed modes such as OCB.
Abstract: We analyze the security of the CTR + CBC-MAC (CCM) encryption mode. This mode, proposed by Doug Whiting, Russ Housley, and Niels Ferguson, combines the CTR (“counter”) encryption mode with CBC-MAC message authentication and is based on a block cipher such as AES. We present concrete lower bounds for the security of CCM in terms of the security of the underlying block cipher. The conclusion is that CCM provides a level of privacy and authenticity that is in line with other proposed modes such as OCB.
4 citations
04 Mar 2019
TL;DR: The main security notion is intended to capture the scenario where a ciphertext obtained under a master key is decrypted by functional keys issued under a different master key, and it is shown there exist simple functional encryption schemes where robustness under adversarial key-generation is not achieved.
Abstract: Robustness is a notion often tacitly assumed while working with encrypted data. Roughly speaking, it states that a ciphertext cannot be decrypted under different keys. Initially formalized in a public-key context, it has been further extended to key-encapsulation mechanisms, and more recently to pseudorandom functions, message-authentication codes and authenticated encryption. In this work, we motivate the importance of establishing similar guarantees for functional encryption schemes, even under adversarially generated keys. Our main security notion is intended to capture the scenario where a ciphertext obtained under a master key (corresponding to Authority 1) is decrypted by functional keys issued under a different master key (Authority 2). Furthermore, we show there exist simple functional encryption schemes where robustness under adversarial key-generation is not achieved. As a secondary and independent result, we formalize robustness for digital signatures – a signature should not verify under multiple keys – and point out that certain signature schemes are not robust when the keys are adversarially generated.
4 citations
Posted Content•
TL;DR: McOE-X and McOE-G as discussed by the authors are two block-cipher-based OAE schemes that are provably secure against noncerespecting and general adversaries.
Abstract: On-Line Authenticated Encryption (OAE) combines privacy with data integrity and is on-line computable. Most block-cipher-based schemes for Authenticated Encryption can be run on-line and are provably secure against nonce-respecting adversaries. But they fail badly for more general adversaries. This is not a theoretical observation only – in practice, the reuse of nonces is a frequent issue. In recent years, cryptographers developed misuse-resistant schemes for Authenticated Encryption. These guarantee excellent security even against general adversaries which are allowed to reuse nonces. But they can not perfom on-line encryption. This work introduces a new family of OAE schemes –called McOE– dealing both with noncerespecting and with general adversaries. Furthermore, we present two block-cipher-based family members, i.e., McOE-X and McOE-G. In contrast to other published OAE, they provably guarantee reasonable security against general adversaries as well as standard security against noncerespecting adversaries.
4 citations