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The universal re-encryption scheme URE and its extension EURE were reviewed,discovering their vulnerabilities to Pfitzmann attack.Then a novel re-encryption scheme WGRe（WonGoo Re-encryption） was proposed.WGRe could en-sure the correctness of the outputs from a node and protect against replay attack,which was hard in layered encryption sys-tems.The experimental results show WGRe is practical and more efficient than URE and EURE schemes due to the fact that its ciphertext is only double the size of the corresponding plaintext,instead of four times as URE or EURE.

Replay attack against MIX was studied and a hybrid-structured onion scheme of MIX against replay attack was proposed.In hybrid scheme, probabilistic encryption and semantic security of universal re-encryption were utilized to protect MIX against replay attack, and the authentication property of layered encryption was utilized to protect integrity of messages.Meanwhile, symmetric encryption was imported to improve efficiency.Analysis shows that the hybrid-structured onion scheme can resist replay attack with guarantee of security and efficiency.

The universal re-encryption scheme URE and its extension EURE were reviewed,discovering their vulnerabilities to Pfitzmann attack.Then a novel re-encryption scheme WGRe（WonGoo Re-encryption） was proposed.WGRe could en-sure the correctness of the outputs from a node and protect against replay attack,which was hard in layered encryption sys-tems.The experimental results show WGRe is practical and more efficient than URE and EURE schemes due to the fact that its ciphertext is only double the size of the corresponding plaintext,instead of four times as URE or EURE.

Replay attack against MIX was studied and a hybrid-structured onion scheme of MIX against replay attack was proposed.In hybrid scheme, probabilistic encryption and semantic security of universal re-encryption were utilized to protect MIX against replay attack, and the authentication property of layered encryption was utilized to protect integrity of messages.Meanwhile, symmetric encryption was imported to improve efficiency.Analysis shows that the hybrid-structured onion scheme can resist replay attack with guarantee of security and efficiency.

Privacy and anonymity on the Internet are gaining increasing attention from both the scientific and the large Internet user community in recent years.Privacy does not only mean the confidentiality of information,but also mean not revealing who is communicating with whom,and how often.After describing the technology of MIX,a survey of ano-nymity technologies based on it was given.Finally WonGoo,a scalable and practical decentralized peer-to-peer protocol was presented that provides strong anonymity and high efficiency with layered encryption and random forwarding.

Privacy and anonymity on the Internet are gaining increasing attention from both the scientific and the large Internet user community in recent years.Privacy does not only mean the confidentiality of information,but also mean not revealing who is communicating with whom,and how often.After describing the technology of MIX,a survey of ano-nymity technologies based on it was given.Finally WonGoo,a scalable and practical decentralized peer-to-peer protocol was presented that provides strong anonymity and high efficiency with layered encryption and random forwarding.