| Summary: | 博士 === 國立成功大學 === 資訊工程學系碩博士班 === 93 === A proxy signature scheme, a variation of ordinary digital signature scheme, enables a proxy signer to sign messages on behalf of the original signer. Proxy signature schemes have been shown to be useful in many applications. For example, a manager can delegate his secretaries to sign documents while he is on vacation. Proxy signature schemes can also be used in electronics transaction and mobile agent environment.
Besides the ordinary proxy signature schemes, many variations were proposed with special properties, such as one-time proxy signature scheme, atomic proxy signature scheme, nominative proxy signature ... etc. Many proxy signature schemes were found to be insecure but some are not. However, we do not know the exactly security of them since they did not provide security proofs.
Recently, the elliptic curve cryptography with bilinear mapping becomes an interesting field. In the field, both certificate-based and identity-based cryptographic schemes are widely discussed. The elliptic curve cryptography becomes a good choice because it reduces the computation cost while remaining the same security level compared with the discrete logarithm computation. The elliptic curve cryptography is also adopted as in IEEE P1363 Standard for public-key cryptography. Several proxy signature schemes are designed based on the bilinear mapping, and enjoy the convenience of the property of bilinear mapping.
In this thesis, we first proposed an intuitive notion of a proxy signature and subsequently proposed a general construction of the intuitive notion. We also proof the security of the security of the proposed proxy signature in random oracle model. More advanced, we proposed a provably secure proxy signature from bilinear mapping and also gave the security proof and performance analysis. To enhance the flexibility of a proxy signature scheme, we also proposed two provably secure proxy signature schemes for compound circumstances. One is for the circumstance that the original signer is in certificate-based key setup while the proxy signer is in identity-based key setup. The other one is for the circumstance counter to the previous one; the original signer is in identity-based key setup while the proxy signer is in certificate-based key setup. Both of them were also given the security proof and performance analysis.
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