• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.123-128
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• 2007

Many service systems use Public Key Infrastructure (PKI) to protect the service. But there arc problems with the use of PKI. One of the problems is that some services would require a function instantaneously to check public kel certificate, but PKI does not satisfy such request. To solve the problem, Bouch et al. first proposed the concept of mediated RSA (mRSA). Then Gene Tsudik proposed 'weak' forward secure mRSA. In this paper, we analyze the weakness of these schemes and find the source of the vulnerabilitv. And we propose a new mRSA that is strong forward secure.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.2
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• pp.327-338
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• 2018

On-line/off-line signature is a technique for performing heavy computations required for signature generation in the off-line stage and completing the final signature by a simple operation in the online stage. This is suitable for application environments that require immediate signing responses to multiple users. In this paper, we propose two new on-line/off-line signature schemes based on RSA problem. The first technique can generate a signature with a fixed base exponentiation when signing online, and the second technique can complete an online signature with a very simple calculation such as a hash operation. The security of both signatures is based on the RSA problem, which is proven to be tightly secure without security loss in the random oracle model.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.42-49
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• 2011

Proxy signature schemes are configured as proxy signers on behalf of their original signers can be allowed to sign messages. Basic security requirements of proxy signature schemes include the strong unforgeability and the verifiability of delegation. So far, a variety of proxy signature schemes that proved on individual basic security terms but not proved on compounded security terms are proposed. Especially the proposed proxy signature schemes based on RSA problem are proved vulnerable to an attacker with his own private key in terms of the impersonating attack. A unauthorized attacker can generate the proxy signature without the appointee's consent or authorization. In this paper, we propose a proxy signature scheme based on RSA problems and warrants that can be proved the security against the impersonating attack. The proposed proxy signature scheme is analyzed on the safety and compared in terms of efficiency with other proxy signature schemes.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1991.11a
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• pp.58-71
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• 1991

본 논문에서는 RSA 암호시스팀의 안전한 암호화, 복호화키의 생성에 관하여 연구하였다. 공개키 암호시스팀인 RSA 암호시스팀은 일반적으로 암호화, 복호화에 요구되는 계산시간과, 안전한 키 생성문제가 중요한 해결과제이다. 안전한 키는 소인수분해 공격에 강한 조건을 만족하는 것이다. 따라서 본 논문에서는 (P$\pm$1) 소인수분해 공격에 강한 조건을 만족하면서, 키 생성시 필요한 $10^{75}$정도의 소수를 예비 소수판정과 소수판정 알고리듬을 사용하여 소수가 아닐 확률이 $10^{-8}$이하가 되도록 하였다. 그리고 생성된 키가 정확함을 입증하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.4
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• pp.951-959
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• 2017

Under the assumption that there is available some additional information other than plaintext-ciphertext pairs, the security of the RSA cryptosystem has been analyzed by the attack methods such as the side-channel attacks and the lattice-based attacks. Recently, based on the data retention property of the powered-off DRAMs, the so called cold boot attack was proposed in the literature, which is focusing on recovering the various cryptosystems' key from some auxiliary information. This paper is dealing with the problem of recovering the RSA private key with erasures and errors and proposes a new key recovery algorithm which is shown to have better performance than the previous one introduced by Kunihiro et al.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.2
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• pp.353-360
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• 1997

In this paper, we propose a new blocking method in which the size of an encryption block is changed according to the size of a message block. The proposed method can be applied to multisignature scheme with no restrictio of the signing order and a multisignature anc be sent secretly to the receiver through RSA encryption. It causes expansion in block size of a multisignuture, but the length of the expanded bits is not greater than the number of signers regardless fo the bit lengths of RSA moduli.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.65-72
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• 2005

Quite recently, Zhou, Lu and Cao proposed a proxy-protected signature scheme based on the RSA assumption and two proxy-protectcd schemes based on the hardness of integer factorization. Dey also provided a security proof for each signature scheme in the random oracle model. In this paper, we show that their schemes do not satisfy a security requirement necessary for proxy signature schemes. This results in generating proxy signature without fay Permission from an original signer.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.1
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• pp.89-97
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• 2000

공개키 암호 시스템 중에서 가장 널리 사용되는 RSA 암호 시스템은 키의 분배와 권리가 용이하고, 디지털 서명이 가능한 장점이 있으나, 암호화와 복호화 과정에서 512 비트 이상의 큰 수에 대한 멱승과 모듈라 감소 연산이 요구되기 때문에 처리 속도의 지연이 큰 문제가 되므로 모듈라 멱승 연산의 고속 처리가 필수적이다. 따라서 본 논문에서는 몫을 추정하여 중간 곱의 크기를 제한하는 interleaved 모듈라 곱셈 기법을 이용하여 모듈라 멱승 연산을 수행하는 고속 RSA 암호 칩을 VHDL을 이용하여 모델링하고 Faraday FG7000A 라이브러리를 이용하여 합성하고 타이밍 검증하여 단일 칩 IC로 구현하였다. 구현된 암호 칩은 75,000 게이트 수준으로 합성되었으며, 동작 주파수는 50MHz이고 1회의 RSA 연산을 수행하는데 소요되는 전체 클럭 사이클은 0.25M이며 512비트 당 처리 속도는 102.4Kbit/s였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.4
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• pp.17-25
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• 2008

Because Chinese Remainder Theorem based RSA (RSA CRT) offers a faster version of modular exponentiation than ordinary repeated squaring, it is promoting with standard. Unfortunately there are major security issues associated with RSA CRT, since Bellcore announced a fault-based cryptanalysis against RSA CRT in 1996. In 1997, Shamir developed a countermeasure using error free immune checking procedure. And soon it became known that the this checking procedure can not effect as the countermeasures. Recently Yen proposed two hardware fault immune protocols for RSA CRT, and this two protocols do not assume the existence of checking procedure. However, in FDTC 2006, the method of attack against the Yen's two protocols was introduced. In this paper, the main purpose is to present a countermeasure against the method of attack from FDTC 2006 for CRT-RSA. The proposed countermeasure use a characteristic bit operation and dose not consider an additional operation.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.3
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• pp.217-223
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• 2009

Recently, the development of the various network method can generate serious social problems. So, it is highly required to control security of network. These problems related security will be developed and keep up to confront with anti-security field such as hacking, cracking. The way to preserve security from hacker or cracker without developing new cryptographic algorithm is keeping the state of anti-cryptanalysis in a prescribed time by means of extending key-length. In this paper, the proposed montgomery multiplication structured unit array method in carry generated part and variable length multiplication for eliminating bottle neck effect with the RSA cryptosystem. Therefore, this proposed montgomery multiplier enforce the real time processing and prevent outer cracking.