Anonymous identity-based encryption (AIBE) is an extension of identity-based encryption (IBE) that enhances the privacy of a ciphertext by providing ciphertext anonymity. In this paper, we introduce the concept of revocable IBE with anonymous revocation (RIBE-AR), which is capable of issuing an update key and hiding the revoked set of the update key that efficiently revokes private keys of AIBE. We first define the security models of RIBE-AR and propose an efficient RIBE-AR scheme in...

In public key encryption (PKE), anonymity is essential to ensure privacy by preventing the ciphertext from revealing the recipient’s identity. However, the literature has addressed the anonymity of PKE under different attack scenarios to a limited extent. Benhamouda et al. (TCC 2020) introduced the first formal definition of anonymity for PKE under corruption, and Huang et al. (ASIACRYPT 2022) made further extensions and provided a generic framework. In this paper, we introduce a new...

Revocable identity-based encryption (RIBE) is an extension of IBE that satisfies a key revocation mechanism to manage a number of users dynamically and efficiently. To resist quantum attacks, two adaptively secure lattice-based RIBE schemes are known in the (quantum) random oracle model ((Q)ROM). Wang et al.'s scheme that is secure in the ROM has large secret keys depending on the depth of a binary tree and its security reduction is not tight. Ma and Lin's scheme that is secure in the QROM...

Revocable hierarchical identity-based encryption (RHIBE) is a variant of the standard hierarchical identity-based encryption (HIBE) satisfying the key revocation functionality. Recently, the first adaptively secure RHIBE scheme with compact ciphertexts was proposed by Emura et al. by sacrificing the efficiency of the schemes for achieving adaptive security so that the secret keys are much larger than Seo and Emura's selectively secure scheme with compact ciphertexts. In this paper, we...

Revocable hierarchical identity-based encryption (RHIBE) is an extension of hierarchical identity-based encryption (HIBE) supporting the key revocation mechanism. In this paper, we propose a generic construction of RHIBE from HIBE with the complete subtree method. Then, we obtain the first RHIBE schemes under the quadratic residuosity assumption, CDH assumption without pairing, factoring Blum integers, LPN assumption, and code-based assumption, and the first almost tightly secure RHIBE...

Revocable hierarchical identity-based encryption (RHIBE) is an extension of HIBE that provides the efficient key revocation function by broadcasting an update key per each time period. Many RHIBE schemes have been proposed by combining an HIBE scheme and the tree-based revocation method, but a generic method for constructing an RHIBE scheme has not been proposed. In this paper, we show for the first time that it is possible to construct RHIBE schemes by generically combining underlying...

Group signature with verifier-local revocation (VLR-GS) is a special type of revocable group sig- nature which enables a user to sign messages without referring to information regarding revoked users. Although there have been several proposals of VLR-GS schemes since the first scheme proposed by Boneh and Shacham [CCS 2004], all of these schemes only achieve a security notion called selfless anonymity, which is strictly weaker than the de facto standard security notion, full anonymity. Thus,...

Revocable identity-based encryption (RIBE) is an extension of identity-based encryption (IBE) and it supports efficient revocation of private keys. In the past, many efficient RIBE schemes have been proposed, but research on efficiently delegating the generation of update keys to a cloud server is somewhat insufficient. In this paper, we newly introduce the concept of delegated RIBE (DRIBE) that can delegate the generation of update keys to the semi-trusted cloud server and define the...

Revocable identity-based encryption (RIBE) is an extension of IBE with an efficient key revocation mechanism. Revocable hierarchical IBE (RHIBE) is its further extension with key delegation functionality. Although there are various adaptively secure pairing-based RIBE schemes, all known hierarchical analogs only satisfy selective security. In addition, the currently known most efficient adaptively secure RIBE and selectively secure RHIBE schemes rely on non-standard assumptions, which are...

We revisit the method of designing public-key puncturable encryption schemes and present a generic conversion by leveraging the techniques of distributed key-distribution and revocable encryption. In particular, we first introduce a refined version of identity-based revocable encryption, named key-homomorphic identity-based revocable key encapsulation mechanism with extended correctness. Then, we propose a generic construction of puncturable key encapsulation mechanism from the former by...

In this paper, we extend the notion of server-aided revocable identity-based encryption (SR-IBE) to the hierarchical IBE (HIBE) setting and propose a generic construction of server-aided revocable hierarchical IBE (SR-HIBE) schemes with decryption key exposure resistance (DKER) from any (weak) L-level revocable HIBE scheme without DKER and (L+1)-level HIBE scheme. In order to realize the server-aided revocation mechanism, we use the “double encryption” technique, and this makes our...

Efficient user revocation has always been a challenging problem in identity-based encryption (IBE). Boldyreva et al. (CCS 2008) first proposed and formalized the notion of revocable IBE (RIBE) based on a tree-based revocation method. In their scheme, each user is required to store a number of long-term secret keys and all non-revoked users have to communicate with the key generation center periodically to update its decryption key. To reduce the workload on the user side, Qin et al....

Revocable identity-based encryption (RIBE) is an extension of IBE which can support a key revocation mechanism, and it is important when deploying an IBE system in practice. Boneh and Franklin (Crypto'01) presented the first generic construction of RIBE, however, their scheme is not scalable where the size of key updates is linear in the number of users in the system. The first generic construction of RIBE is presented by Ma and Lin with complete subtree (CS) method by combining IBE and...

As an extension of identity-based encryption (IBE), revocable hierarchical IBE (RHIBE) supports both key revocation and key delegation simultaneously, which are two important functionalities for cryptographic use in practice. Recently in PKC 2019, Katsumata et al. constructed the first lattice-based RHIBE scheme with decryption key exposure resistance (DKER). Such constructions are all based on bilinear or multilinear maps before their work. In this paper, we simplify the construction of...

To deal with dynamically changing user's credentials in identity-based encryption (IBE), providing an efficient key revocation method is a very important issue. Recently, Ma and Lin proposed a generic method of designing a revocable IBE (RIBE) scheme that uses the complete subtree (CS) method by combining IBE and hierarchical IBE (HIBE) schemes. In this paper, we propose a new generic method for designing an RIBE scheme that uses the subset difference (SD) method instead of using the CS...

Revocable identity-based encryption (RIBE) is an extension of IBE that supports a key revocation mechanism, which is important when deployed an IBE system in practice. Boneh and Franklin presented the first generic construction of RIBE, however, their scheme is not scalable where the size of key update is linear in the number of users in the system. Then, Boldyreva, Goyal and Kumar presented the first scalable RIBE where the size of key update is logarithmic in the number of users and linear...

Identity-based broadcast encryption (IBBE) is an effective method to protect the data security and privacy in multi-receiver scenarios, which can make broadcast encryption more practical. This paper further expands the study of scalable revocation methodology in the setting of IBBE, where a key authority releases a key update material periodically in such a way that only non-revoked users can update their decryption keys. Following the binary tree data structure approach, a concrete ...

Revocable identity-based encryption (RIBE) is an extension of IBE that supports a key revocation mechanism; an indispensable feature for practical cryptographic schemes. Due to this extra feature, RIBE is often required to satisfy a strong security notion unique to the revocation setting called decryption key exposure resistance (DKER). Additionally, hierarchal IBE (HIBE) is another orthogonal extension of IBE that supports key delegation functionalities allowing for scalable deployments of...

In this paper, we present an identity-based encryption scheme from codes with efficient key revocation. Recently, in Crypto 2017, Gaborit et al. proposed a first identity-based encryption scheme from codes with rank metric, called RankIBE. To extract the decryption key from any public identity, they constructed a trapdoor function which relies on RankSign, a signature scheme proposed by Gaborit et al. in PQCrypto 2014. We adopt the same trapdoor function to add efficient key revocation...

In this paper, we propose an efficient revocable Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme. We base on the direct revocation approach, by embedding the revocation list into ciphertext. However, since the revocation list will grow longer as time goes by, we further leverage this by proposing a secret key time validation technique so that users will have their keys expired on a date and the revocation list only needs to include those user keys revoked before their intended...

Ciphertext Policy Attribute-Based Encryption (CP- ABE) has been proposed to implement the attribute-based access control model. In CP-ABE, data owners encrypt the data with a certain access policy such that only data users whose attributes satisfy the access policy could obtain the corresponding private decryption key from a trusted authority. Therefore, CP-ABE is considered as a promising fine-grained access control mechanism for data sharing where no centralized trusted third party exists,...

Ciphertext-Policy Attribute-Based Encryp- tion (CP-ABE) is an access control mechanism over encrypted data and well suited for secure group-based communication. However, it also suffers from the fol- lowing problem, i.e., it is impossible to build all de- sired groups. For example, if two group members have exactly the same attributes, how to construct a group including only one of the two members? Obviously, at- tributes alone cannot distinguish these two members, therefore existing CP-ABE...

We consider the problems of i) using public-key encryption to enforce dynamic access control on clouds; and ii) key rotation of data stored on clouds. Historically, proxy re-encryption, ciphertext delegation, and related technologies have been advocated as tools that allow for revocation and the ability to cryptographically enforce \emph{dynamic} access control on the cloud, and more recently they have suggested for key rotation of data stored on clouds. Current literature frequently...

In general, identity-based encryption (IBE) does not support an efficient revocation procedure. In ACM CCS'08, Boldyreva et al. proposed revocable identity-based encryption (RIBE), which enables us to efficiently revoke (malicious) users in IBE. In PKC 2013, Seo and Emura introduced an additional security notion for RIBE, called decryption key exposure resistance (DKER). Roughly speaking, RIBE with DKER guarantees that the security is not compromised even if an adversary gets (a number of)...

Revoking corrupted users is a desirable functionality for cryptosystems. Since Boldyreva, Goyal, and Kumar (ACM CCS 2008) proposed a notable result for scalable revocation method in identity-based encryption (IBE), several works have improved either the security or the efficiency of revocable IBE (RIBE). Currently, all existing scalable RIBE schemes that achieve adaptively security against decryption key exposure resistance (DKER) can be categorized into two groups; either with long public...

Server-aided revocable identity-based encryption (SR-IBE), recently proposed by Qin et al. at ESORICS 2015, offers significant advantages over previous user revocation mechanisms in the scope of IBE. In this new system model, almost all the workloads on users are delegated to an untrusted server, and users can compute decryption keys at any time period without having to communicate with either the key generation center or the server. In this paper, inspired by Qin et al.’s work, we design...

Hierarchical identity-based encryption (HIBE) can be extended to revocable HIBE (RHIBE) if a private key of a user can be revoked when the private key is revealed or expired. Previously, many selectively secure RHIBE schemes were proposed, but it is still unsolved problem to construct an adaptively secure RHIBE scheme. In this work, we propose two RHIBE schemes in composite-order bilinear groups and prove their adaptive security under simple static assumptions. To prove the adaptive...

At EUROCRYPT 2012, Libert, Peters and Yung (LPY) proposed the first scalable revocable group signature (R-GS) scheme in the standard model which achieves constant signing/verification costs and other costs regarding signers are at most logarithmic in N, where N is the maximum number of group members. However, although the LPY R-GS scheme is asymptotically quite efficient, this scheme is not sufficiently efficient in practice. For example, the signature size of the LPY scheme is roughly 10...

Revocable hierarchical identity-based encryption (RHIBE) is an extension of HIBE that supports the revocation of user's private keys to manage the dynamic credentials of users in a system. Many different RHIBE schemes were proposed previously, but they are not efficient in terms of the private key size and the update key size since the depth of a hierarchical identity is included as a multiplicative factor. In this paper, we propose efficient RHIBE schemes with shorter private keys and...

Hierarchical identity-based encryption (HIBE) is an extension of identity-based encryption (IBE) where an identity of a user is organized as a hierarchical structure and a user can delegate the private key generation to another user. Providing a revocation mechanism for HIBE is highly necessary to keep a system securely. Revocable HIBE (RHIBE) is an HIBE scheme that can revoke a user's private key if his credential is expired or revealed. In this paper, we first propose an unbounded HIBE...

In view of the expiration or reveal of user's private credential (or private key) in a realistic scenario, identity-based encryption (IBE) schemes with an efficient key revocation mechanism, or for short, revocable identity-based encryption (RIBE) schemes, become prominently significant. In this paper, we present an RIBE scheme from lattices by combining two Agrawal et al.'s IBE schemes with the subset difference (SD) method. Our scheme is secure against adaptive identity-time attacks in the...

Identity-based encryption (IBE) eliminates the necessity of having a costly certificate verification process. However, revocation remains as a daunting task in terms of ciphertext update and key update phases as due to the lack of a certificate revocation list in this infrastructure. In this paper, we provide an affirmative solution to solve the efficiency problem incurred by revocation. We propose the first cloud-based revocable identity-based proxy re-encryption (CR-IB-PRE) scheme that...

Providing an efficient revocation mechanism for identity-based encryption (IBE) is very important since a user's credential (or private key) can be expired or revealed. Revocable IBE (RIBE) is an extension of IBE that provides an efficient revocation mechanism. Previous RIBE schemes essentially use the complete subtree (CS) scheme of Naor, Naor and Lotspiech (CRYPTO 2001) for key revocation. In this paper, we present a new technique for RIBE that uses the efficient subset difference (SD)...

A revocation mechanism in cryptosystems for a large number of users is absolutely necessary for maintaining the security of whole systems. A revocable identity-based encryption (RIBE) provides an efficient revocation method in IBE in which a trusted authority periodically broadcasts an update key for non-revoked users and a user can decrypt a ciphertext if his private key is not revoked in the update key. Boldyreva, Goyal, and Kumar (CCS 2008) defined RIBE and proposed an RIBE scheme that...

Identity-based encryption (IBE) has been regarded as an attractive alternative to more conventional certificate-based public key systems. It has recently attracted not only considerable research from the academic community, but also interest from the industry and standardization bodies. However, while key revocation is a fundamental requirement to any public key systems, not much work has been done in the identity-based setting. In this paper, we continue the study of revocable IBE (RIBE)...

In the public key cryptosystems, revocation functionality is required when a secret key is corrupted by hacking or the period of a contract expires. In the public key infrastructure setting, numerous solutions have been proposed, and in the Identity Based Encryption (IBE) setting, a recent series of papers proposed revocable IBE schemes. Delegation of key generation is also an important functionality in cryptography from a practical standpoint since it allows reduction of excessive workload...

In ACM CCS 2008, Boldyreva et al. proposed an elegant way of achieving an Identity-based Encryption (IBE) with {\em efficient} revocation, which we call revocable IBE (RIBE). One of the significant benefit of their construction is scalability, where the overhead of the trusted authority is logarithmically increased in the number of users, whereas that in the Boneh-Franklin naive revocation way is linearly increased. All subsequent RIBE schemes follow the Boldyreva et al. security model and...

In this paper, we present an identity-based encryption (IBE) scheme from lattices with efficient key revocation. We adopt multiple trapdoors from the Agrawal-Boneh-Boyen and Gentry-Peikerty-Vaikuntanathan lattice IBE schemes to realize key revocation, which in turn, makes use of binary-tree data structure. Using our scheme, key update requires logarithmic complexity in the maximal number of users and linear in the number of revoked users for the relevant key authority. We prove that our...

Since there always exists some users whose private keys are stolen or expired in practice, it is important for identity based encryption (IBE) system to provide a solution for revocation. The current most efficient revocable IBE system has a private key of size $\mathcal{O}(\log n)$ and update information of size $\mathcal{O}(r \log(\frac{n}{r}))$ where $r$ is the number of revoked users. We describe a new revocable IBE systems where the private key only contains two group elements and the...