Abstract The threshold cryptography provides a new approach to building intrusion tolerance
applications. In this paper, a threshold decryption scheme based elliptic curve cryptography is presented.
A zero-knowledge test approach based on elliptic curve cryptography is designed. The application of
these techniques in Web security is studied. Performance analysis shows that our scheme is characterized
by excellent security as well as high efficiency.
Key words intrusion tolerance; elliptic curve cryptography; threshold decryption; web
security

Despite all the defenses, some of the attacks will
inevitably be successful. We must build intrusion
tolerant systems that can operate through these attacks.
The threshold cryptography provides new
methodology for developing intrusion tolerance system.
The research on the threshold cryptography based
intrusion tolerance techniques concentrate on threshold
encryption, threshold decryption, threshold
authentication and threshold signature. Generally,
threshold encryption and threshold decryption are
based on the cryptography algorithms, which are
homomorphic, such as RSA. The homomorpohic
property is necessary in order to generate shares of the
key so that partial cryptograms can be combined into a
cryptogram for the correct message[1]. Therefore,
nearly all projects studying on threshold cryptography
techniques focused on the homomorphic algorithm.
Among these, the intrusion tolerance via threshold
cryptography (ITTC) project developed by Stanford
University is notable, which researched and
developed the intrusion tolerance application based
on threshold RSA[2].
Currently, elliptic curve cryptography (ECC) is
regarded as an attractive cryptography that can
provide greater strength, higher speed and smaller
keys than other cryptography systems[3,4]. Therefore,
the research on threshold ECC deserves great
attention. However, ECC is not homomorphic. It is
difficult to design ECC-based threshold schemes. So,
there are not many public published papers or
reports on ECC-based threshold schemes, especially
on ECC-based threshold encryption or decryption
schemes. In this paper, we present an ECC based
threshold decryption scheme and a zero-knowledge
test approach. And we apply our research results in
building intrusion tolerant Web security system.