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. One drawback of encrypting data is that it can be selectively shared only at a coarse-grained level (i.e., giving another party your private key). We describe a new concept for fine-grained sharing of encrypted data that we call Attribute-Based Encryption (ABE). In ABE, ciphertexts are labeled with sets of attributes and private keys are associated with access structures that control which ciphertexts a user is able to decrypt. We demonstrate the applicability of ABE to sharing of audit-log information and broadcast encryption. We describe a construction that supports delegation of private keys, which subsumes Hierarchical Identity-Based Encryption (HIBE).