Delegation system for decryption rights
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United States of America Patent
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N/A
Issued Date -
Jul 17, 2008
app pub date -
Aug 21, 2007
filing date -
Aug 22, 2006
priority date (Note) -
Abandoned
status (Latency Note)
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Abstract
An object of this ciphertext decryption rights delegation system is to enable conversion of PKE-system ciphertext into IBE-system encrypted ciphertext, and, in a delegation system with users using only an IBE system, of preventing restoration of the master-secret key generated by a PKG device (public key generation device) even when there is collusion attack between the ciphertext converter and a decryption rights delegatee. A ciphertext decryption rights delegation system realizes delegation of ciphertext decryption rights between a device used by a decryption rights delegator and a device used by a decryption rights delegatee. From the master-secret key stored in the PKG device which generates secret keys, a secret key of the IBE system and auxiliary information are generated, and a re-encryption key is generated based on this auxiliary information. When sharing content, ciphertext encrypted by the decryption rights delegator device is converted by a ciphertext conversion device using the re-encryption key, and the converted ciphertext is decoded by the decryption rights delegatee device using the IBE-system secret key.
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