## CryptoDB

### Yupu Hu

#### Publications

Year
Venue
Title
2016
EUROCRYPT
2015
EPRINT
2015
EPRINT
2015
EPRINT
2010
EPRINT
It is a difficult task to compute the $r$-th order nonlinearity of a given function with algebraic degree strictly greater than $r>1$. Even the lower bounds on the second order nonlinearity is known only for a few particular functions. We investigate the lower bounds on the second order nonlinearity of cubic Boolean functions $F_u(x)=Tr(\sum_{l=1}^{m}\mu_{l}x^{d_{l}})$, where $u_{l} \in F_{2^n}^{*}$, $d_{l}=2^{i_{l}}+2^{j_{l}}+1$, $i_{l}$ and $j_{l}$ are positive integers, $n>i_{l}> j_{l}$. Especially, for a class of Boolean functions $G_u(x)=Tr(\sum_{l=1}^{m}\mu_{l}x^{d_{l}})$, we deduce a tighter lower bound on the second order nonlinearity of the functions, where $u_{l} \in F_{2^n}^{*}$, $d_{l}=2^{i_{l}\gamma}+2^{j_{l}\gamma}+1$, $i_{l}> j_{l}$ and $\gamma\neq 1$ is a positive integer such that $gcd(n,\gamma)=1$. \\The lower bounds on the second order nonlinearity of cubic monomial Boolean functions, represented by $f_\mu(x)=Tr(\mu x^{2^i+2^j+1})$, $\mu\in F_{2^n}^*$, $i$ and $j$ are positive integers such that $i>j$, have recently (2009) been obtained by Gode and Gangopadhvay. Our results have the advantages over those of Gode and Gangopadhvay as follows. We first extend the results from monomial Boolean functions to Boolean functions with more trace terms. We further generalize and improve the results to a wider range of $n$. Also, our bounds are better than those of Gode and Gangopadhvay for monomial functions $f_\mu(x)$.
2006
EPRINT
Signcryption is a cryptographic primitive that performs signature and encryption simultaneously, at a lower computational costs and communication overheads than the signature-then-encryption approach. In this paper, we propose an efficient multi-recipient signcryption scheme based on the bilinear pairings which broadcasts a message to multiple users in a secure and authenticated manner. We prove its semantic security and unforgeability under the Gap Diffie-Hellman problem assumption in the random oracle model. The proposed scheme is more efficient than re-signcrypting a message n times using a signcryption scheme in terms of computational costs and communication overheads.

#### Coauthors

Juntao Gao (1)
Huiwen Jia (4)
Fagen Li (1)
Xuelian Li (1)
Shuanggen Liu (1)