dabenc_adapt_hybrid

Hybrid Encryption Adapter for Multi-Authority ABE (MA-ABE Hybrid)

Description: Converts a Decentralized/Multi-Authority Attribute-Based Encryption scheme into a hybrid encryption scheme capable of encrypting arbitrary-length messages.

Notes: Uses symmetric encryption (AES) with a randomly generated session key.

The session key is encrypted using the underlying Multi-Authority ABE scheme.

Adapter Properties

• Type: hybrid encryption adapter

• Underlying Scheme: any Decentralized/Multi-Authority ABE scheme

• Purpose: enables Multi-Authority ABE schemes to encrypt arbitrary-length byte messages

Implementation

Authors:

10. Ayo Akinyele

Date:

2011

class dabenc_adapt_hybrid.HybridABEncMA(scheme, groupObj)

Bases: ABEncMultiAuth

>>> from charm.toolbox.pairinggroup import PairingGroup,GT
>>> group = PairingGroup('SS512')
>>> dabe = Dabe(group)

Setup master authority.

>>> hyb_abema = HybridABEncMA(dabe, group)
>>> global_parameters = hyb_abema.setup()

Generate attributes for two different sub-authorities: Johns Hopkins University, and Johns Hopkins Medical Institutions.

>>> jhu_attributes = ['jhu.professor', 'jhu.staff', 'jhu.student']
>>> jhmi_attributes = ['jhmi.doctor', 'jhmi.nurse', 'jhmi.staff', 'jhmi.researcher']

Johns Hopkins sub-authorities master key.

>>> (jhu_secret_key, jhu_public_key) = hyb_abema.authsetup(global_parameters, jhu_attributes)

JHMI sub-authorities master key

>>> (jhmi_secret_key, jhmi_public_key) = hyb_abema.authsetup(global_parameters, jhmi_attributes)

To encrypt messages we need all of the authorities’ public keys.

>>> allAuth_public_key = {};
>>> allAuth_public_key.update(jhu_public_key);
>>> allAuth_public_key.update(jhmi_public_key)

An example user, Bob, who is both a professor at JHU and a researcher at JHMI.

>>> ID = "20110615 bob@gmail.com cryptokey"
>>> secrets_keys = {}
>>> hyb_abema.keygen(global_parameters, jhu_secret_key,'jhu.professor', ID, secrets_keys)
>>> hyb_abema.keygen(global_parameters, jhmi_secret_key,'jhmi.researcher', ID, secrets_keys)

Encrypt a message to anyone who is both a profesor at JHU and a researcher at JHMI.

>>> msg = b'Hello World, I am a sensitive record!'
>>> policy_str = "(jhmi.doctor or (jhmi.researcher and jhu.professor))"
>>> cipher_text = hyb_abema.encrypt(global_parameters, allAuth_public_key, msg, policy_str)
>>> hyb_abema.decrypt(global_parameters, secrets_keys, cipher_text)
b'Hello World, I am a sensitive record!'

authsetup(gp, attributes)

Setup an authority. :param gp: The global parameters of the scheme. :param object: Additional required arguments, for example a list of attributes or a name. :return: The result of the authority setup.

decrypt(gp, sk, ct)

Decrypt a ciphertext. :param gp: The global parameters of the scheme. :param sk: The secret keys of the user. :param ct: The ciphertext to decrypt. :return: The plaintext. :raise Exception: Raised when the attributes do not satisfy the access policy.

encrypt(gp, pk, M, policy_str)

Encrypt a message. :param gp: The global parameters of the scheme. :param pk: The public keys of all relevant authorities. :param m: The message to encrypt. :param object: An access policy or a set of attributes to use. :return: The encrypted message.

keygen(gp, sk, i, gid, pkey)

Generate user secret keys for attributes from a single authority. :param gp: The global parameters of the scheme. :param sk: The secret keys of the attribute authority. :param gid: Global identifier for the user. :param object: An attribute, list of attributes or access structure, depending on the scheme. :return: The secret keys for the user for the given attributes/access structure.

setup()

Setup this multi-authority attribute based encryption scheme. :return: The result of the central setup, for example some global parameters.

dabenc_adapt_hybrid.main()