Description

There is a trend for sensitive user data to be stored by third parties on the Internet. Attribute-based encryption (ABE) can be used for log encryption. Instead of encrypting each part of a log with the keys of all recipients, it is possible to encrypt the log only with attributes which match recipient’s attributes. This primitive can also be used for broadcast encryption in order to decrease the number of keys used. As more sensitive data is shared and stored by third-party sites on the Internet, there will be a need to encrypt data stored at these sites. In this project the system proposes generic constructions of CPA-secure and RCCA-secure ABE systems with verifiable outsourced decryption from CPA-secure ABE with outsourced decryption. At a high level, in order to construct such ABE schemes with verifiable outsourced decryption, the system begin with a CPA secure ABE scheme with outsourced decryption. The system also instantiate our CPA-secure construction in the standard model and then show an implementation of this instantiation. In this CPA-secure construction, unlike the technique of separately encrypting an extra random message and then using this random message to commit to the true message in this method is encrypting a message and a random value together and then committing to the message by using the random value. Our construction is generic and has smaller ciphertext size and less computational costs. It also makes us obtain generic RCCA-secure construction more naturally.