On privacy protection data publication targeting dynamic data, a privacy issue for the generalization property called m-invariance has been pointed out. In this paper, we propose an information alteration method to overcome this issue.

Bitcoin is one of the typical cryptocurrencies. Cur-rently, Bitcoin allows unilateral sending of currency by the sender (payer of currency) regardless of the presence or absence of intention of the recipient (payee of currency). Previous works pointed out that this could induce the sending of currency used in crimes, etc., which could lead to problems. This problem is called the recipient unapproved problem. Bitcoin users use a function called Bitcoin wallet in the platform software such as Bitcoin Core to perform transactions. In this paper, we try to incorporate a new transaction creation method into the Bitcoin wallet in order to resolve the recipient unapproved problem. The new transaction creation method also allows the recipient's Bitcoin wallet to participate in the creation of the transaction, and adds the recipient's digital signature to prove that the transaction was also approved by the recipient and a new address that cannot be used except for approved transactions. In experiments for investigating the overhead of the new transaction creation method, results showed that a transaction can be created with about twice creation execution time of the conventional transaction creation method.

On information security area, it is important to guarantee data privacy, availability and integrity. Secret sharing schemes are known as technologies for protecting data privacy and attaining availability. In secret sharing schemes, n distributed informations of a secret value d, called as shares are constructed, and distributed those to n participants. Then, a group of t members for n participants reconstruct the secret value d by exchanging their shares each other. On the other hand, less than t shares cannot induce the secret value. Moreover, as secret sharing schemes for solving the issue for data integrity, there exist verifiable secret sharing schemes. In verifiable secret sharing schemes, we can also confirm the correctness of reconstructed secrets. In this paper, we focus on a previous verifiable secret sharing scheme and point out issues as necessity of multi-party computations to protect shares from malicious participants. Next, we propose a new verifiable secret sharing scheme without multi-party computations and prove the security of verifications by the proposed scheme.

In recent years, blockchain is known as a decentralized secure digital ledger of economic transactions. In this paper, we point out a new issue by abusing published information with relation to recipients on blockchain. Then, we propose a solution to our discovered issue.

Let $G=(V,E)$ be an edge‐weighted undirected graph with n vertices and m edges. We present a deterministic algorithm to compute a minimum k‐way cut of G for a given k. Our algorithm is a divide‐and‐conquer method based on a procedure that reduces an instance of the minimum k‐way cut problem to $O(n^{2k-5})$ instances of the minimum $(\lfloor (k+\sqrt{k})/2\rfloor+1)$‐way cut problem, and can be implemented to run in $O(n^{4k/(1-1.71/\sqrt{k}) -31} )$ time. With a slight modification, the algorithm can find all minimum k‐way cuts in $O(n^{4k/(1-1.71/\sqrt{k}) -16} )$ time.

Given an undirected graph G with n vertices, m edges and positive edge weights and k terminals {s/sub 1/, s/sub 2/, ..., s/sub k/} on G, the problem of computing a minimum k-way cut of G is to find a minimum (cost) k-way cut C that disconnects each terminal from all the others. The minimum k-way cut problem is known as NP-hard even if all vertex degrees are three or less and k is equal to 3. The minimum k-way cut problem for a planar graph and fixed integer k can be solved in polynomial time. This paper presents an algorithm for computing a minimum three-way cut of a graph in a larger class than planar graphs.>