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During the Coincheck incident, which recorded the largest damages in cryptocurrency history in 2018, it was demonstrated that using Mosaic token can have a certain effect. Although it seems attractive to employ tokens as countermeasures for cryptocurrency leakage, Mosaic is a specific token for the New Economy Movement (NEM) cryptocurrency and is not employed for other blockchain systems or cryptocurrencies. Moreover, although some volunteers tracked leaked NEM using Mosaic in the CoinCheck incident, it would be better to verify that the volunteers can be trusted. Simultaneously, if someone (e.g., who stole cryptocurrencies) can identify the volunteers, then that person or organization may be targets of them. In this paper, we propose an anonymous trust-marking scheme on blockchain systems that is universally applicable to any cryptocurrency. In our scheme, entities called token admitters are allowed to generate tokens adding trustworthiness or untrustworthiness to addresses. Anyone can anonymously verify whether these tokens were issued by a token admitter. Simultaneously, only the designated auditor and no one else, including nondesignated auditors, can identify the token admitters. Our scheme is based on accountable ring signatures and commitment, and is implemented on an elliptic curve called Curve25519, and we confirm that both cryptographic tools are efficient. Moreover, we also confirm that our scheme is applicable to Bitcoin, Ethereum, and NEM., An extended abstract appeared at the 3rd IEEE International Conference on Blockchain and Cryptocurrency, ICBC 2021. This is the full version

In an open-bid auction, a bidder can know the budgets of other bidders. Thus, a sealed-bid auction that hides bidding prices is desirable. However, in previous sealed-bid auction protocols, it has been difficult to provide a ``fund binding'' property, which would guarantee that a bidder has funds more than or equal to the bidding price and that the funds are forcibly withdrawn when the bidder wins. Thus, such protocols are vulnerable to false bidding. As a solution, many protocols employ a simple deposit method in which each bidder sends a deposit to a smart contract, which is greater than or equal to the bidding price, before the bidding phase. However, this deposit reveals the maximum bidding price, and it is preferable to hide this information. In this paper, we propose a sealed-bid auction protocol that provides a fund binding property. Our protocol not only hides the bidding price and a maximum bidding price, but also provides fund binding, simultaneously. For hiding the maximum bidding price, we pay attention to the fact that usual Ethereum transactions and transactions for sending funds to a one-time address have the same transaction structure, and it seems that they are indistinguishable. We discuss how much bidding transactions are hidden. We also employ DECO (Zhang et al,. CCS 2020) that proves the validity of the data to a verifier in which the data are taken from a source without showing the data itself. Finally, we give our implementation which shows transaction fees required and compare it to a sealed-bid auction protocol employing the simple deposit method.

This paper introduces a new capability for group signatures called message-dependent opening. It is intended to weaken the high trust placed on the opener; i.e., no anonymity against the opener is provided by an ordinary group signature scheme. In a group signature scheme with message-dependent opening (GS-MDO), in addition to the opener, we set up an admitter that is not able to extract any user’s identity but admits the opener to open signatures by specifying messages where signatures on the specified messages will be opened by the opener. The opener cannot extract the signer’s identity from any signature whose corresponding message is not specified by the admitter. This paper presents formal definitions of GS-MDO and proposes a generic construction of it from identity-based encryption and adaptive non-interactive zero-knowledge proofs. Moreover, we propose two specific constructions, one in the standard model and one in the random oracle model. Our scheme in the standard model is an instantiation of our generic construction but the message-dependent opening property is bounded. In contrast, our scheme in the random oracle model is not a direct instantiation of our generic construction but is optimized to increase efficiency and achieves the unbounded message-dependent opening property. Furthermore, we also demonstrate that GS-MDO implies identity-based encryption, thus implying that identity-based encryption is essential for designing GS-MDO schemes.

In recent years, increasingly many companies have entered the pay-as-you-go business because it has become easier to monitor services constantly due to the development and increase in the number of Internet of Things (IoT) devices. Research is in progress to introduce cryptographic assets into the payment, but if a private key is stolen, the cryptographic assets associated with it can be stolen. To address this issue, this paper proposes a secure automated payment system using contract wallets. This method ensures the security of cryptographic assets even if the private key is stolen. Secure automated payments are enabled by issuing transactions from IoT devices and using internal transactions to link contract wallets and smart contracts that handle the payment of cryptographic assets. Furthermore, the effectiveness of the proposed system is demonstrated on the Ethereum blockchain as a proof of concept, and the cost of gas is measured.

A ledger can be defined as a “book of permanent record.” With modern information technology, data have become economic resources if they are associated with exclusive owners and put into a ledger. It is shown in Chaps. 3 and 4 that IoT data can be transformed into productive resources while Chaps. 5 and 6 show that transaction data can be turned into money-like bank deposit currencies.

Availability is very important for long-term use of wireless sensor networks WSNs, assuming the presence of an attacker. It is thus important to achieve secure communication among WSNs even if some sensor nodes are compromised. Self-healing WSNs possess the feature that a network automatically self-heals after node-capture attacks in order to achieve availability. The self-healing means that the ratio of compromised links decreases with time, even if the attacker corrupts sensor nodes of the network. In this paper, three kinds of self-healing schemes for WSNs are described, a polynomial-based self-healing scheme, a simple random key pre-distribution scheme with self-healing, and a proactive co-operative link self-healing scheme. Our contributions are the self-healing schemes with security evaluation, in which we conduct analytical evaluation and a simulation experiment of our schemes, and results obtained from both analysis and simulations indicate that our schemes are effective in self-healing. Furthermore, comparing three schemes, we clarify each difference and discuss optimal scheme under each different environments. © 2015 The Authors. Concurrency and Computation: Practice and Experience Published by John Wiley & Sons Ltd.

In this paper, we propose an efficient and optimally secure sensor network aggregation protocol against multiple corrupted nodes by a random-walk adversary. Our protocol achieves one round-trip communication to satisfy optimal security without the result-checking phase, by conducting aggregation along with the verification, based on the idea of TESLA technique. Furthermore, we show that the congestion complexity, communication complexity and computational cost in our protocol are constant, i.e., O(1).

I n this paper 1 , we propose a strongly resilient polynomial-based random key pre-distribution scheme for multi- phase wireless sensor networks (RPoK): a private sub-key is not directly stored in each sensor node by applying the polynomial- based scheme to the RoK scheme. Such a polynomial is linearly transformed using forward and backward keys in order to achieve the forward and backward security of polynomials. As a result, our scheme achieves a large reduction of the ratio of compromised links by enhancing the security of the previous RoK scheme. The results obtained analytically and by simulations show that our scheme can dramatically improve the ratio of compromised links compared with the RoK scheme. I. INTRODUCTION

Security software such as anti-virus software and personal firewall are usually installed in every host within an enterprise network. There are mainly two kinds of security software: signature-based software and anomaly-based software. Anomaly-based software generally has a “threshold” that discriminates between normal traffic and malware communications in network traffic observation. Such a threshold involves the number of packets used for behavior checking by the anomaly-based software. Also, it indicates the number of packets sent from an infected host before the infected host is contained. In this paper, we propose a mathematical model that uses discrete mathematics known as combinatorics, which is suitable for situations in which there are a small number of infected hosts. Our model can estimate the threshold at which the number of infected hosts can be suppressed to a small number. The result from our model fits very well with the result of computer simulation using typical existing scanning malware and a typical network.

In key-recovery methods using smart cards, a user can recover the disk encryption key in cooperation with the system administrator, even if the user has lost the smart card including the disk encryption key. However, the disk encryption key is known to the system administrator in advance in most key-recovery methods. Hence user's disk data may be read by the system administrator. Furthermore, if the disk encryption key is not known to the system administrator in advance, it is difficult to achieve a key authentication. In this paper, we propose a scheme which enables to recover the disk encryption key when the user's smart card is lost. In our scheme, the disk encryption key is not preserved anywhere and then the system administrator cannot know the key before key-recovery phase. Only someone who has a user's smart card and knows the user's password can decrypt that user's disk data. Furthermore, we measured the processing time required for user authentication in an experimental environment using a virtual machine monitor. As a result, we found that this processing time is short enough to be practical.

Recently, cryptographic schemes based on the user's attributes have been proposed. An Attribute-Based Group Signature (ABGS) scheme is a kind of group signature schemes, where a user with a set of attributes can prove anonymously whether she has these attributes or not. An access tree is applied to express the relationships among some attributes. However, previous schemes do not provide the changing an access tree. In this paper, we propose a Dynamic ABGS scheme that enables an access tree to be changed. Our ABGS is efficient in that re-issuing of the attribute certificate previously issued for each user is not necessary. Moreover, calculations depending on the number of attributes are calculated on the domain of a pairing. Therefore, the number of calculations in a pairing does not depend on the number of attributes associated with a signature. Finally, we discuss how our ABGS can be applied to an anonymous survey for collection of attribute statistics.

An Attribute-Based Encryption (ABE) is an encryption scheme, where users with some attributes can decrypt ciphertexts associated with these attributes. However, the length of the ciphertext depends on the number of attributes in previous ABE schemes. In this paper, we propose a new Ciphertext-Policy Attribute-Based Encryption(CP-ABE) with constant ciphertext length. Moreover, the number of pairing computations is also constant., Proceedings of the 5th International Conference, ISPEC 2009 Xi’an, China, April 13-15, 2009.

If there are many displaced workers in a company, then a person who goes for job hunting might not select this company. That is, the number of members who quit is quite negative information. Similarly, in revocable group signature schemes, if one knows (or guesses) the number of revoked users (sayr), then one may guess the reason behind such circumstances, and it may lead to harmful rumors. However, no previous revocation procedure can achieve hidingr. In this paper, we propose the first revocable group signature scheme, whereris kept hidden, which we callr-hiding revocable group signature. To handle this property, we newly define the security notion called anonymity with respect to the revocation which guarantees the unlinkability of revoked users.

スズは鋼の機械的性質等に影響を及ぼすため，その含有率を正確に定量する必要があるが，微量域のスズを高い精度と感度で定量できる化学分析法はない．本研究では，アノードストリッピングボルタンメトリーを応用し，鉄マトリックス共存下で簡便迅速にスズが定量できる酸分解直接分析法を開発した．スズ(IV)の還元電着には多量の臭化物の共存が必要であり，鉄(III)の妨害はL(+)-アスコルビン酸で鉄(II)へ還元することにより除去できた．2 mol dm−3臭化ナトリウムと0.2 mol dm−3L(+)-アスコルビン酸を含む0.3 mol dm−3塩酸–0.1 mol dm−3硝酸中，−0.5 V vs. Ag/AgClで300秒間前電解して回転金膜電極上にスズを電着後，40 mV s−1の速度で示差パルスモードにより電位を0 V vs. Ag/AgClまで走査して析出物を溶出させた．1000 μg cm−3鉄(II)存在下，スズ(IV)濃度8.4 × 10−9–3.4 × 10−7 mol dm−3の範囲で原点を通る直線の検量線が得られた．20 ng cm−3スズ(IV)での相対標準偏差(n = 5)および検出限界(3σ)は，それぞれ4.3%，2.8 × 10−9 mol dm−3であった．カドミウム(II)と銅(II)は定量に妨害した．鉄鋼中120–400 μg g−1のスズを高い精度と正確さで，50分以内に定量できた．本法は，市中スクラップ鉄中1 μg−1以上のスズの定量に適用可能であり，予備濃縮操作を必要とする現行JIS化学分析法に比べて定量下限が1けた以上低下した．

In INFOCOM 2010, Pietro, Oligeri, Soriente, and Tsudik (POST) proposed an intrusion-resilient system with forward and backward secrecy in mobile Unattended Wireless Sensor Networks (UWSNs), where sensors move according to some mobility model (random jump model and random waypoint model). In the POST scheme, each sensor encrypts its ephemeral key $K$ as a plaintext by using the sink's public key, and sends this cipher text and the encrypted sensed data by $K$. Although the POST scheme recommends the hybrid encryption, it does not follow the conventional hybrid encryption usage, i.e., the POST scheme is not necessarily secure. More concretely, $K$ must be regarded as a plaintext of the underlying public key system, and therefore the POST scheme requires at least one more encryption procedure (i.e, encryptions for both $K$ and the data) compared with the conventional hybrid encryption procedure. In this paper, we scrutinize the original POST intrusion-resilient system. We set deployed information as a seed used for generating a random number (which is applied for public key encryption). This procedure follows the conventional hybrid encryption usage, and random-number-leakage problem does not occur. In conclusion, we improve the POST scheme from the viewpoint of both security and efficiency without spoiling significant benefit points of the original one.

Virtual Machine Monitors (VMMs), also called hypervisors, can be used to construct a trusted computing base (TCB) enhancing the security of existing operating systems. The complexity of a VMM-based TCB causes the high risk of security vulnerabilities. Therefore, this paper proposes a two-step execution mechanism to reduce the complexity of a VMM-based TCB. We propose a method to separate a conventional VMM-based TCB into the following two parts: (1) A thin hypervisor with security services and (2) A special guest OS for security preprocessing. A special guest OS performing security tasks can be executed in advance. After shutting down the special guest OS, a hypervisor obtains preprocessing security data and next boots a target guest OS to be protected. Thus, the proposed two-step execution mechanism can reduce run-time codes of a hypervisor. This paper shows a design, a prototype implementation and measurement results of lines of code using BitVisor, a VMM-based TCB we have developed.

Information leakage has recently become a serious problem. Because a user's disk might contain a lot of confidential information, it should be encrypted and the encryption key protected securely. Disk security has been improved by storing the encryption key in a hardware token such as a smart card or USB device. There must be some way to recover the encryption key when the token is lost, but to prevent information leakage the encryption key should not be known by the system administrator and should not be able to be recovered by malicious users inside the system. Here we describe a scheme that can limit key recovery when the user's smart card is lost and can do so without the administrator knowing the key. The smart card is used for generating the key and for improving the user authentication.