Keonwoo Kim

GPU-Accelerated Password Cracking of PDF Files

Digital document file such as Adobe Acrobat or MS-Office is encrypted by its own ciphering algorithm with a user password. When this password is not known to a user or a forensic inspector, it is necessary to recover the password to open the encrypted file. Password cracking by brute-force search is a perfect approach to discover the password but a time consuming process. This paper presents a new method of speeding up password recovery on Graphic Processing Unit (GPU) using a Compute Unified Device Architecture (CUDA). PDF files are chosen as a password cracking target, and the Abode Acrobat password recovery algorithm is examined. Experimental results show that the proposed method gives high performance at low cost, with a cluster of GPU nodes significantly speeding up the password recovery by exploiting a number of computing nodes. Password cracking performance is increased linearly in proportion to the number of computing nodes and GPUs.

Visual Analysis of Portable Computer Forensic Data

From the portable computer forensic data represented in a tabular form with the same pattern, it is not easy to find out features about user behaviors or draw relationships between data. Especially, it is almost impossible to detect the meaningful forensic evidences from the collected tabular-form data when large amounts of data are acquired and multiple data are needed to be analyzed at the same time. In this paper, we propose intuitive and visual analysis of forensic events using a graphic element not a tabular form to represent efficiently and meaningfully the collected portable forensic data.

A new fingerprinting codes for multimedia contents

Digital fingerprinting is a technology for enforcing digital rights policies where by unique labels, known as digital fingerprints, are inserted into content prior to distribution. As we use it, we can trace illegal users. These fingerprints are typically embedded into the content using watermarking techniques that are designed to be robust to a variety of attacks. Also, it must secure against collusion attack that some colluders remove and alter their fingerprints. In this paper, we propose easily fingerprint generation technique by using trace of primitive polynomial. The proposed scheme can generate codes more easily and have more buyers than existing schemes. Our scheme is secure against collusion attack with two colluders. And we proposed a new watermarking algorithm that embeds and extracts securely by using MPSK(M-ary Phase Shift Keying) technology. The proposed watermarking algorithm has semi-robustness. Therefore it is effective in conspirator detection.

Performance Analysis of Format-Preserving Encryption Based on Unbalanced-Feistel Structure

Format-Preserving Encryption (FPE) is used to produce a ciphertext with the same length and format as a plaintext. Some approaches to do that are a prefix cipher, a cycle walking, a feistel network and so on. In this paper, we present format-preserving encryption using the unbalanced-feistel structure. We apply our construction to FFX, VAES3 and BPS schemes, which are modes of operation for FPE. We also analyze the performance of three unbalanced-feistel FPE schemes over block ciphers. VAES3 using 128-bit AES encrypts credit card numbers at 5,924,000bps.