Ku-Young Chang

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We determine all the non-abelian normal CM-fields of degree 24 with class number one, provided that the Galois group of their maximal real subfields is isomorphic to A4, the alternating group of degree 4 and order 12. There are two such fields with Galois group A4 × C2 (see Theorem 14) and at most one with Galois group SL2(F3) (see Theorem 18); if the(More)
Let N be an imaginary abelian number field. We know that h − N , the relative class number of N , goes to infinity as f N , the conductor of N , approaches infinity, so that there are only finitely many imaginary abelian number fields with given relative class number. First of all, we have found all imaginary abelian number fields with relative class number(More)
In this paper, we consider some aspects of binding properties that bind an anonymous user with messages. According to whether all the messages or some part of the messages are bound with an anonymous user, the protocol is said to satisfy the full binding property or the partial binding property, respectively. We propose methods to combine binding properties(More)
In this paper we propose an efficient OT N 1 scheme in the bounded storage model, which is provably secure without complexity assumptions. Under the assumption that a public random string of M bits is broadcasted, the protocol is secure against any computationally unbounded dishonest receiver who can store τ M bits, τ < 1. The protocol requires the sender(More)
A ring signature scheme provides signer ambiguity by hiding a signer in a ring of arbitrary members appropriately. A convertible ring signature scheme is an extension of a ring signature scheme that authenticates a signer and proves that a real signer and no one else generated a ring signature. In this paper, we first show that the recent convertible ring(More)