Certificate-based encryption (CBE) is a new asymmetric encryption paradigm which was introduced to solve the certificate management problem in traditional public key encryption (PKE). It combines PKE and identity-based encryption (IBE) while preserving some of their most attractive features. CBE provides an efficient implicit certificate mechanism which eliminates the third-party queries and si...

A key recovery attack allows an attacker to recover the private key of an underlying encryption scheme when given a number of decryption oracle accesses. Previous research has shown that most existing Somewhat Homomorphic Encryption (SHE) schemes suffer from this attack. In this paper, we propose efficient key recovery attacks against two NTRU-based SHE schemes, which have not gained much atten...

The Twofish AES submission document contains a partial chosen-key and a related-key attack against ten rounds of Twofish without whitening, using 256-bit keys. This attack does not work; it makes use of a postulated class of weak key pairs which has the S-box keys and eight successive round keys equal, but no such pairs exist. In this report we analyze the occurrence of this kind of weak key pa...

A group oriented encryption scheme is presented in this paper. In this scheme, a sender is allowed to encrypt a message using the group public key and send the ciphertext to the group. Any user in the group can independently decrypt the ciphertext via his private key. The scheme is secure against adaptively chosen ciphertext attack and collude attack.

We show that a recently proposed construction by Rosen and Segev can be used for obtaining the first public key encryption scheme based on the McEliece assumptions which is secure against adaptive chosen ciphertext attacks in the standard model.

At PKC 2003 Paeng, Jung, and Ha proposed a lattice based public key cryptosystem(PJH). It is originated from GGH, and designed as a hybrid of GGH and NTRUEncrypt in order to reduce the key size. They claimed that PJH is secure against all possible attacks, especially against lattice attacks. However, in this paper, we present a key recovery attack, based on lattice theory, against PJH. The runn...

An enhanced authentication key exchange protocol was proposed to exchange multiple session keys between two participants at a time. This paper shows that this enhanced protocol is insecure under the known session key attack, known long-term private key attack, signature forgery attack, and replay attack. This paper also proposes an enhanced and secure key agreement protocol for exchanging multi...

TCHo is a public key encryption scheme based on a stream cipher component, which is particular suitable for low cost devices like RFIDs. In its basic version, TCHo offers no IND-CCA2 security, but the authors suggest to use a generic hybrid construction to achieve this security level. The implementation of this method however, significantly increases the hardware complexity of TCHo and thus ann...