Signcryption from Randomness Recoverable PKE Revisited (original) (raw)
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Provably Secure Identity-based Aggregate Signcryption Scheme in Random Oracles
2015
This article proposes a provably secure aggregate signcryption scheme in random oracles. Security of the scheme is based on computational infesibility of solving Decisional Bilinear Diffie-Hellman Problem and Discrete Logarithm Problems. Confidentiality and authenticity are two fundamental security requirement of Public key Cryptography. These are achieved by encryption scheme and digital signatures respectively. Signcryption scheme is a cryptographic primitive that performs signature and encryption simultaneously in a single logical steps. An aggregate signcryption scheme can be constructed of the aggregation of individual signcryption. The aggreagtion is done taking n distinct signcryptions on n messages signed by n distinct users.
Provable Secure Identity Based Signcryption Schemes without Random Oracles
International Journal of Network Security & Its Applications, 2012
Signcryption is a cryptographic primitive which performs encryption and signature in a single logical step with the cost lower than signature-then-encryption approach. Recently, Li et al. [35] proposed the first provable secure identity based signcryption without random oracles. In their scheme sender signs the ciphertext. However, in [11] Boyen showed that non-repudiation is easily achieved if the sender sign the plaintext rather than ciphertext. In this paper we proposed an identity based signcryption scheme without random oracles, which provides the non-repudiation with respect to plaintext. We also proposed an identity based public verifiable signcryption scheme with third party verification in the standard model.
A Revocable ID-based Signcryption Scheme
J. Inf. Hiding Multim. Signal Process., 2012
Signcryption scheme can efficiently perform encryption and signing procedures in a single step to obtain message confidentiality and non-reputation properties. As compared to the traditional public key system, identity (ID)-based public key system (IDPKS) can simplify the management of required certificates. However, how to revoke these compromised or misbehaving identities in the IDPKS becomes a critical problem. Recently, Tseng and Tsai proposed a novel construction in the IDPKS with revocation mechanism called revocable ID-based public key system (R-IDPKS). In this paper, we follow their R-IDPKS to propose an important cryptographic primitive ”signcryption”. Security analysis is made to demonstrate that the proposed scheme is provably secure and provides confidentiality and unforgeability.
Security of verifiably encrypted signatures and a construction without random oracles
Pairing-Based CryptographyPairing 2009, 2009
In a verifiably encrypted signature scheme, signers encrypt their signature under the public key of a trusted third party and prove that they did so correctly. The security properties, due to Boneh et al. (Eurocrypt 2003), are unforgeability and opacity. This paper proposes two novel fundamental requirements for verifiably encrypted signatures, called extractability and abuse-freeness, and analyzes its effects on the established security model. Extractability ensures that the trusted third party is always able to extract a valid signature from a valid verifiably encrypted signature and abuse-freeness guarantees that a malicious signer, who cooperates with the trusted party, is not able to forge a verifiably encrypted signature. We further show that both properties are not covered by the model of Boneh et al. The second main contribution of this paper is a verifiably encrypted signature scheme, provably secure without random oracles, that is more efficient and greatly improves the public key size of the only other construction in the standard model by Lu et al. (Eurocrypt 2006). Moreover, we present strengthened definitions for unforgeability and opacity in the spirit of strong unforgeability of digital signature schemes.
On the Provable Security of Multi-Receiver Signcryption Schemes
In ATC 2007, an identity based signcryption scheme for multiple receivers was proposed by Yu et al. In this paper, we first show that Yu et al.'s signcryption scheme is insecure by demonstrating an universal forgeability attack -anyone can generate a valid signcryption on any message on behalf of any legal user for any set of legal receivers without knowing the secret keys of the legal users. Also, we point out a subtle flaw in the proof of confidentiality given by Yu et al. and show that the scheme does not provide confidentiality. Further, we propose a corrected version of Yu et al.'s scheme and formally prove its security (confidentiality and unforgeability) under the existing security model for signcryption.
A New Signature Scheme without Random Oracles and Its Applications
2008
In this paper, we propose a new signature scheme that is existentially unforgeable under a chosen message attack without random oracle. The security of our scheme depends on a new complexity assumption called the k+1 square roots assumption. We also discuss the relationship between the k+1 square roots assumption and some related problems and provide some conjectures. Moreover, the k+1 square roots assumption can be used to construct shorter signatures under the random oracle model. As some applications, a new chameleon hash signature scheme and a on-line/off-line signature scheme and a new efficient anonymous credential scheme based on the proposed signature scheme are presented.
eprint.iacr.org
Verifiably encrypted signature schemes (VES) allow a signer to encrypt his or her signature under the public key of a trusted third party, while maintaining public signature verifiability. With our work, we propose two generic constructions based on Merkle authentication trees that do not require non-interactive zero-knowledge proofs (NIZKs) for maintaining verifiability. Both are stateful and secure in the standard model. Furthermore, we extend the specification for VES, bringing it closer to real-world needs. We also argue that statefulness can be a feature in common business scenarios. Our constructions rely on the assumption that CPA (even slightly weaker) secure encryption, "maskable" CMA secure signatures, and collision resistant hash functions exist. "Maskable" means that a signature can be hidden in a verifiable way using a secret masking value. Unmasking the signature is hard without knowing the secret masking value. We show that our constructions can be instantiated with a broad range of efficient signature and encryption schemes, including two lattice-based primitives. Thus, VES schemes can be based on the hardness of worstcase lattice problems, making them secure against subexponential and quantum-computer attacks. Among others, we provide the first efficient pairing-free instantiation in the standard model.
On the Security of Identity Based Ring Signcryption Schemes
Lecture Notes in Computer Science, 2009
Signcryption is a cryptographic primitive which offers authentication and confidentiality simultaneously with a cost lower than signing and encrypting the message independently. Ring signcryption enables a user to signcrypt a message along with the identities of a set of potential senders (that includes him) without revealing which user in the set has actually produced the signcryption. Thus a ring signcrypted message has anonymity in addition to authentication and confidentiality. Ring signcryption schemes have no group managers, no setup procedures, no revocation procedures and no coordination: any user can choose any set of users (ring), that includes himself and signcrypt any message by using his private and public key as well as other users (in the ring) public keys, without getting any approval or assistance from them. Ring Signcryption is useful for leaking trustworthy secrets in an anonymous, authenticated and confidential way.
Identity Based Public Verifiable Signcryption Scheme
2010
Signcryption as a cryptographic primitive that offers both confidentiality and authentication simultaneously. Generally, in signcryption schemes, the message is hidden and thus the validity of the signcryption can be verified only after the unsigncryption process. Thus, a third party will not be able to verify whether the signcryption is valid or not. Signcryption schemes that allow any one to verify the validity of signcryption without the knowledge of the message are called public verifiable signcryption schemes. Third party verifiable signcryption schemes allow the receiver of a signcryption, to convince a third party that the signcryption is valid, by providing some additional information along with the signcryption. This information can be anything other than the receiver’s private key and the verification may or may not require the exposure of the corresponding message. This paper shows the security weaknesses in two such existing schemes namely [14] and [4]. The scheme in [14] is Public Key Infrastructure (PKI) based scheme and the scheme in [4] is an identity based scheme. More specifically, [14] is based on elliptic curve digital signature algorithm (ECDSA). We also, provide a new identity based signcryption scheme that provides both public verifiability and third party verification. We formally prove the security of the newly proposed scheme in the random oracle model.