• Bulletin of the Korean Mathematical Society
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• v.51 no.5
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• pp.1347-1356
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• 2014

In this paper, we analyze the security of the KMOV public key cryptosystem. KMOV is based on elliptic curves over the ring $\mathbb{Z}_n$ where n = pq is the product of two large unknown primes of equal bit-size. We consider KMOV with a public key (n, e) where the exponent e satisfies an equation ex-(p+1)(q+1)y = z, with unknown parameters x, y, z. Using Diophantine approximations and lattice reduction techniques, we show that KMOV is insecure when x, y, z are suitably small.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.3
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• pp.3-10
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• 2000

In this paper we propose a bit-sliced modular multiplication algorithm and a bit-sliced modular multiplier design meeting the increasing crypto-key size for RSA public key cryptosystem. The proposed bit-sliced modular multiplication algorithm was designed by modifying the Montgomery's algorithm. The bit-sliced modular multiplier is easy to expand to process large size operands and can be immediately applied to RSA public key cryptosystem.

• Review of KIISC
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• v.1 no.1
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• pp.130-143
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• 1991

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.6
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• pp.1492-1511
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• 2013

A novel, chaotic map that is based on concatenated torus automorphisms is proposed in this paper. As we know, cat map, which is based on torus automorphism, is highly chaotic and is often used to encrypt information. But cat map is periodic, which decreases the security of the cryptosystem. In this paper, we propose a novel chaotic map that concatenates several torus automorphisms. The concatenated mechanism provides stronger chaos and larger key space for the cryptosystem. It is proven that the period of the concatenated torus automorphisms is the total sum of each one's period. By this means, the period of the novel automorphism is increased extremely. Based on the novel, concatenated torus automorphisms, two application schemes in image encryption are proposed, i.e., 2D and 3D concatenated chaotic maps. In these schemes, both the scrambling matrices and the iteration numbers act as secret keys. Security analysis shows that the proposed, concatenated, chaotic maps have strong chaos and they are very sensitive to the secret keys. By means of concatenating several torus automorphisms, the key space of the proposed cryptosystem can be expanded to $2^{135}$. The diffusion function in the proposed scheme changes the gray values of the transferred pixels, which makes the periodicity of the concatenated torus automorphisms disappeared. Therefore, the proposed cryptosystem has high security and they can resist the brute-force attacks and the differential attacks efficiently. The diffusing speed of the proposed scheme is higher, and the computational complexity is lower, compared with the existing methods.

• Journal of the Korea Society of Computer and Information
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• v.8 no.2
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• pp.112-121
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• 2003

Information Protection and cryptography technology is developed with if but solved problem of real time processing and secret maintain. Therefore this paper is Proposed new PRN-SEED(Pseudo-Random Number-SEED) for the increasing secret rate and processing rate perform performance analysis with existed other cryptography algorithms. Proposed new PRN-SEED crypto-algorithm increase in the processing rate than existed algorithms use bit and byte mixed operation with RNG(Random Number Generator). PRN-SEED that performs simultaneous operations have higher 1.03 in the processing rate and 2 in the cryptosystem performance than existed cryptosystems. Implementation for PRN-SEED use Synopsys Design Analyser Ver. 1999.10, samsung KG75 library and Synopsys VHDL Debegger. As a simulation result, symmetric cryptosystem DES operate 416Mbps at the 40MHz and Rijndael operate 612Mbps at the 50MHz. PRN-SEED cryptosystem have gate counting 10K and operate 430Mbps at the 40MHz and 630Mbps at the 50MHz.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.5_6
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• pp.239-249
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• 2003

The secret sharing is the basic concept of the threshold cryptosystem and has an important position in the modern cryptography. At 1995, Jarecki proposed the proactive secret sharing to be a solution of existing the mobile adversary and also proposed the share renewal scheme for (k, n) threshold scheme. For n participants in the protocol, his method needs $O(n^2)$ modular exponentiation per one participant. It is very high computational cost and is not fit for the scalable cryptosystem. In this paper, we propose the efficient share renewal scheme that need only O(n) modular exponentiation per participant. And we prove our scheme is secure if less than img ${\frac{1}{2}}$ n-1 adversaries exist and they are static adversary.

• Current Optics and Photonics
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• v.3 no.2
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• pp.119-127
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• 2019

A new secret-key-sharing cryptosystem using optical phase-shifting digital holography is proposed. The proposed secret-key-sharing algorithm is based on the Diffie-Hellman key-exchange protocol, which is modified to an optical cipher system implemented by a two-step quadrature phase-shifting digital holographic encryption method using orthogonal polarization. Two unknown users' private keys are encrypted by two-step phase-shifting digital holography and are changed into three digital-hologram ciphers, which are stored by computer and are opened to a public communication network for secret-key-sharing. Two-step phase-shifting digital holograms are acquired by applying a phase step of 0 or ${\pi}/2$ in the reference beam's path. The encrypted digital hologram in the optical setup is a Fourier-transform hologram, and is recorded on CCDs with 256 quantized gray-level intensities. The digital hologram shows an analog-type noise-like randomized cipher with a two-dimensional array, which has a stronger security level than conventional electronic cryptography, due to the complexity of optical encryption, and protects against the possibility of a replay attack. Decryption with three encrypted digital holograms generates the same shared secret key for each user. Schematically, the proposed optical configuration has the advantage of producing a kind of double-key encryption, which can enhance security strength compared to the conventional Diffie-Hellman key-exchange protocol. Another advantage of the proposed secret-key-sharing cryptosystem is that it is free to change each user's private key in generating the public keys at any time. The proposed method is very effective cryptography when applied to a secret-key-exchange cryptosystem with high security strength.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.33 no.1
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• pp.13-31
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• 2023

Korean Government-PKI (GPKI) is a public-key infrastructure which provides authentication and security functions for information system used by central government, local governments, and public institutions of the Republic of Korea to provide their own administrative and public services. The current cryptosystem of GPKI was established in the early 2000s, and more than ten years have passed since the last improvement in 2010. Over the past decade or so, the information security, including cryptography, has undergone many changes and will continue to face many changes. Therefore, for the sustainable security of GPKI, it is necessary to review the security of the cryptosystem at this point. In this paper, we analyze the current status and the security of technologies and standards used in the system. We identify cryptographic algorithms with degraded security, international standards which are obsoleted or updated, and cryptographic parameters that should be revised for the high security level. And based on this, we make several suggestions on the reorganization of cryptographic algorithms and related technologies for the security enhancement of GPKI.

• 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.

• Journal of Internet Computing and Services
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• v.4 no.3
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• pp.1-8
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• 2003

The power analysis attack is a physical attack which can be applied to the cryptosystems such as smartcard. We try to experimental attack to a smart card which implemented Elliptic Curve Cryptosystem adopting NAF algorithm as a secret key recording method. Our differential power analysis attack is a potential threat to that implementation. The attacker measures the power traces during the multiplication with secret key bits in a target smart card and the multiplication with the guessed bits in other experimental one. The comparison of these two traces gives a secret bit, which means that attacker can find all secret key bits successively.