arXiv subjects

Bagus Santoso

Publications and source records attributed to Bagus Santoso.

10 recordsLinked to original sources

arXiv2026

A Framework of Variable-Length Source Encryption using Mutual Information Security Criterion: Universal Coding, Strong Converse Theorem

In this paper we consider the variable-length lossless source coding for discrete memoryless sources. We proposes a new encryption framework for securely transmitting codewords over a noiseless channel. The proposed source encryption framework is based on the secure communication framework of the Shannon cipher system. In the proposed framework, we use the mutual information as a measure of information leakage to an adversary. We establish the necessary and sufficient condition for secure communication under the condition that the information leakage is upper bounded by a constant $δ\in (0,\infty)$, thereby providing a complete solution to the problem. We also show that the obtained necessary and sufficient condition does not depend on the constant $δ\in (0,\infty)$, demonstrating that we have the strong converse coding theorem for the proposed framework of source encryption. We further prove the existence of encryption/decryption schemes, which are universal in the sense that they work effectively for any distributions of the plain text and those of the key used for the encryption.

cs.IT↗

arXiv2026

A Framework of Secure Source Coding using Mutual Information Security Criterion: Universal Coding, Strong Converse Theorem

In this paper, we propose a framework of source encryption, where cryptographic processing is applied to a prescribed fixed length source code. The proposed source encryption framework is based on the secure communication framework of the Shannon cipher system. In the proposed framework, we use the mutual information as a measure of information leakage to an adversary. For the proposed framework, we explicitly establish the necessary and sufficient condition for reliable and secure communication under the condition that error probability and information leakage, respectively, are upper bounded by prescribed constants $ε\in (0,1)$ and $δ\in (0,\infty)$. We also show that the obtained necessary and sufficient condition does not depend on the constants $ε\in (0,1)$ and $δ\in (0,\infty)$, demonstrating that we have the strong converse theorem for the proposed framework of source encryption. We further prove the existence of encryption/decryption schemes, which are universal in the sense that they work effectively for any distributions of the plain text and those of the key used for the encryption.

cs.IT↗

arXiv2026

A Framework of Distributed Source Encryption using Mutual Information Security Criterion and the Strong Converse Theorem

We reinvestigate the general distributed secure source coding based on the common key cryptosystem proposed by Oohama and Santoso (ITW 2021). They proposed a framework of distributed source encryption and derived the necessary and sufficient conditions to have reliable and secure transmission. However, the bounds of the rate region, which specifies both necessary and sufficient conditions to have reliable and secure transmission under the proposed cryptosystem, were derived based on a self-tailored non-standard} security criterion. In this paper we adopt the standard security criterion, i.e., standard mutual information. We successfully establish the bounds of the rate region based on this security criterion. Information spectrum method and a variant of Birkhoff-von Neumann theorem play an important role in deriving the result.

cs.IT↗

arXiv2024

Universal Coding for Shannon Ciphers under Side-Channel Attacks

We study the universal coding under side-channel attacks posed and investigated by Oohama and Santoso (2022). They proposed a theoretical security model for Shannon cipher system under side-channel attacks, where the adversary is not only allowed to collect ciphertexts by eavesdropping the public communication channel, but is also allowed to collect the physical information leaked by the devices where the cipher system is implemented on such as running time, power consumption, electromagnetic radiation, etc. For any distributions of the plain text, any noisy channels through which the adversary observe the corrupted version of the key, and any measurement device used for collecting the physical information, we can derive an achievable rate region for reliability and security such that if we compress the ciphertext with rate within the achievable rate region, then: (1) anyone with secret key will be able to decrypt and decode the ciphertext correctly, but (2) any adversary who obtains the ciphertext and also the side physical information will not be able to obtain any information about the hidden source as long as the leaked physical information is encoded with a rate within the rate region.

cs.IT↗

arXiv2022

New Distributed Source Encryption Framework

We pose and investigate the distributed secure source coding based on the common key cryptosystem. This cryptosystem includes the secrecy amplification problem for distributed encrypted sources with correlated keys using post-encryption-compression, which was posed investigated by Santoso and Oohama. In this paper we propose another new security criterion which is generally more strict compared to the commonly used security criterion which is based on the upper-bound of mutual information between the plaintext and the ciphertext. Under this criterion, we establish the necessary and sufficient condition for the secure transmission of correlated sources.

cs.IT↗

arXiv2022

Three-Pass Identification Scheme Based on MinRank Problem with Half Cheating Probability

In Asiacrypt 2001, Courtois proposed the first three-pass zero-knowledge identification (ID) scheme based on the MinRank problem. However, in a single round of Courtois' ID scheme, the cheating probability, i.e., the success probability of the cheating prover, is 2/3 which is larger than half. Although Courtois also proposed a variant scheme which is claimed to have half cheating probability, its security is not formally proven and it requires another hardness assumption on a specific one-way function and that verifier always generates challenges according to a specific non-uniform distribution. In this paper, we propose the first three-pass zero-knowledge ID scheme based on the MinRank problem with the cheating probability of exactly half for each round, even with only two-bit challenge space, without any additional assumption. Our proposed ID scheme requires fewer rounds and less total average communications costs compared to Curtois' under the same security level against impersonation.

cs.CR↗

arXiv2022

Strong Converse Theorem for Source Encryption under Side-Channel Attacks

We are interested in investigating the security of source encryption with a symmetric key under side-channel attacks. In this paper, we propose a general framework of source encryption with a symmetric key under the side-channel attacks, which applies to \emph{any} source encryption with a symmetric key and \emph{any} kind of side-channel attacks targeting the secret key. We also propose a new security criterion for strong secrecy under side-channel attacks, which is a natural extension of mutual information, i.e., \emph{the maximum conditional mutual information between the plaintext and the ciphertext given the adversarial key leakage, where the maximum is taken over all possible plaintext distribution}. Under this new criterion, we successfully formulate the rate region, which serves as both necessary and sufficient conditions to have secure transmission even under side-channel attacks. Furthermore, we also prove another theoretical result on our new security criterion, which might be interesting in its own right: in the case of the discrete memoryless source, no perfect secrecy under side-channel attacks in the standard security criterion, i.e., the ordinary mutual information, is achievable without achieving perfect secrecy in this new security criterion, although our new security criterion is more strict than the standard security criterion.

cs.IT↗

arXiv2019

Information Theoretic Security for Broadcasting of Two Encrypted Sources under Side-Channel Attacks

We consider the secure communication problem for broadcasting of two encrypted sources. The sender wishes to broadcast two secret messages via two common key cryptosystems. We assume that the adversary can use the side-channel, where the side information on common keys can be obtained via the rate constraint noiseless channel. To solve this problem we formulate the post encryption coding system. On the information leakage on two secrete messages to the adversary, we provide an explicit sufficient condition to attain the exponential decay of this quantity for large block lengths of encrypted sources.

cs.IT↗

arXiv2019

Information Theoretic Security for Side-Channel Attacks to the Shannon Cipher System

We study side-channel attacks for the Shannon cipher system. To pose side channel-attacks to the Shannon cipher system, we regard them as a signal estimation via encoded data from two distributed sensors. This can be formulated as the one helper source coding problem posed and investigated by Ahlswede, Körner(1975), and Wyner(1975). We further investigate the posed problem to derive new secrecy bounds. Our results are derived by a coupling of the result Watanabe and Oohama(2012) obtained on bounded storage evasdropper with the exponential strong converse theorem Oohama(2015) established for the one helper source coding problem.

cs.IT↗

arXiv2018

Secrecy Amplification for Distributed Encrypted Sources with Correlated Keys using Affine Encoders

This paper proposed the application of post-encryption-compression (PEC) to strengthen the secrecy in the case of distributed encryption where the encryption keys are correlated to each other. We derive the universal code construction for the compression and the rate region where codes with achievability and secrecy are obtainable. Our main technique is to use affine encoders which are constructed from certain linear encoders to encode the ciphertexts before sending them to public communication channels. We show that if the rates of linear codes are within a certain rate region:(1) information leakage on the original sources from the encoded ciphertexts without the keys is negligible, while (2) one who has legitimate keys is able to retrieve the original source data with negligible error probability.

cs.IT↗