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The quantum adder is a vital arithmetic operation for quantum algorithms. However, the existing quantum floating-point adders only considered the case of two normal numbers. In this paper, we propose an enhanced quantum floating-point adder based on IEEE 754 standard. First, we divide quantum floating-point adders into four cases: the normal case, subnormal case, mixed case, and special case. Then, we propose a result-sign and mantissa-sign determining unit to avoid conversion from sign-magnitude to two complements. Moreover, we design a new quantum leading zero detector with the optimized T-depth and T-count. Comparison results reveal that the proposed floating-point adder has lower circuit width, T-depth, and T-count than the current works. [ABSTRACT FROM AUTHOR]

Recently, Tang, Carlet and Tang presented a combinatorial conjecture about binary strings, allowing proving that all balanced functions in some infinite class they introduced have optimal algebraic immunity. Later, Cohen and Flori completely proved that the conjecture is true. These functions have good (provable or at least observable) cryptographic properties but they are not 1-resilient, which represents a drawback for their use as filter functions in stream ciphers. We propose a construction of an infinite class of 1-resilient Boolean functions with optimal algebraic immunity by modifying the functions in this class. The constructed functions have optimal algebraic degree, that is, meet the Siegenthaler bound, and high nonlinearity. We prove a lower bound on their nonlinearity, but as for the Carlet-Feng functions and for the functions mentioned above, this bound is not enough for ensuring a nonlinearity sufficient for allowing resistance to the fast correlation attack. Nevertheless, as for previously found functions with the same features, there is a gap between the bound that we can prove and the actual values computed for small numbers of variables. Our computations show that the functions in this class have very good nonlinearity and also good immunity to fast algebraic attacks. This is the first time that an infinite class of functions gathers all of the main criteria allowing these functions to be used as filters in stream ciphers. [ABSTRACT FROM AUTHOR]

Identity-based signcryption is a primitive that combines the functions of identity-based encryption and identity-based signature. In this paper, we first attack two of the existing identity-based signcryption schemes which are claimed to be provably secure without random oracles. Then we construct a new identity-based signcryption scheme and proves its security without random oracles. [ABSTRACT FROM AUTHOR]

In this paper, we establish a general connection between authentication codes and difference balanced functions. Consequently, we present three new classes of authentication codes without secrecy from difference balanced functions. This is the first time that the difference balanced functions, which were used in literature mainly to construct sequences with good correlations, have been used to construct authentication codes. [ABSTRACT FROM AUTHOR]