A METHOD FOR ATTRIBUTE BASED BROADCAST ENCRYPTION WITH PERMANENT REVOCATION

• US 20140226816A1
• Filed: 08/22/2012
• Published: 08/14/2014
• Est. Priority Date: 08/24/2011
• Status: Active Grant

• Current Assignee: Ben Gurion University of The Negev, Sami Shamoon College Of Engineering
• Original Assignee: Ben Gurion University of The Negev, Sami Shamoon College Of Engineering
• Inventors: Dolev, Shlomi, Gilboa, Niv, Kopeetsky, Marina
• Granted Patent: US 9,413,528 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04L 2209/601 Broadcast encryption
• CPC Class Codes: H04L 9/0816 Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
• CPC Class Codes: H04L 9/0833 involving conference or group key network architectures or network communication protocols for key management in group communication in a packet data network H04L63/065
• CPC Class Codes: H04L 9/0866 involving user or device identifiers, e.g. serial number, physical or biometrical information, DNA, hand-signature or measurable physical characteristics
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/3073 involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing
• CPC Class Codes: H04N 21/2347 involving video stream encryption
• CPC Class Codes: H04N 21/26606 for generating or managing entitlement messages, e.g. Entitlement Control Message [ECM] or Entitlement Management Message [EMM] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/4405 involving video stream decryption
• CPC Class Codes: H04N 21/4623 Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14

Abstract

The invention is a method for broadcast encryption that allows a broadcaster to send encrypted data to a set of users such that only a subset of authorized users can decrypt said data. The method comprises modifications to the four stages of the basic Cipher-text Policy Attribute-Based Encryption techniques. The method can be adapted to transform any Attribute-Based Encryption scheme that supports only temporary revocation into a scheme that supports the permanent revocation of users.

Claims

1. A method for broadcast encryption that allows a broadcaster to send encrypted data to a set of users such that only a subset of authorized users can decrypt said data, wherein said method supports permanent revocation of users;

said method comprising the following modifications to the four stages of the basic Cipher-text Policy Attribute-Based Encryption techniques;

a) in the setup stage—

a random control component is added by said broadcaster to the master key;

b) in the key generation stage—

said broadcaster sends to each user a private key that includes the attributes of said user and a component that includes the state of said user, wherein said state of said user is a function of said random control component;

c) in the encrypt stage;

said broadcaster constructs a ciphertext by use of an algorithm that includes a global secret key, wherein said global secret key is encrypted by said private keys of said subset of authorized users; and

d) in the decrypt stage;

the broadcaster sends said ciphertext which encrypts said global secret key to said authorized users, whereupon only users in said subset of authorized users are able to decrypt and use said global secret key.

2. The method of claim 1 in which, if one or more users is admitted to or revoked from the subset of authorized users, thereby forming a new subset of authorized users:

a) the broadcaster updates the random control component to a new random control component;

thereby,

b) changing the master key and the state of each user and their private keys;

thereby,

c) changing the global secret key to a new global secret key, which is encrypted by the private keys of said new subset of authorized users;

thereby,

d) only allowing users in said new subset of authorized users to decrypt ciphertext that has been encrypted by said broadcaster using an algorithm that includes said new global secret key; and

therefore,

e) only allowing users in said new subset of authorized users to use said new global secret key.

3. The method of claim 1, wherein said method is adapted to transform any Attribute-Based Encryption scheme that supports only temporary revocation into a scheme that supports the permanent revocation of users.