NTT Research, Inc.

The present disclosure relates to a computerized method and system for message encryption in a multi-user setting. The method involves receiving a message of arbitrary length for each user, storing the message in a computerized data store, and executing a setup to generate a master secret and public keys. A random variable is generated, and a function is defined based on this variable. A second secret is derived using a functional encryption scheme, resulting in a derived secret. The message is encrypted by generating a first random string, a second partially random string, and a ciphertext. The system also includes a method for decrypting the encrypted message, processing the derived secret and ciphertext to derive a string, and deriving a plaintext message from this string.

The present disclosure provides a method for randomized multi-input functional encryption. A setup processor generates, for each input, a component for generating a proof, public-private key pairs, an obfuscated program for verifying ciphertexts and outputting a proof, and an encryption key. The setup processor generates a master secret key and transmits encryption keys to an encryption processor and the master secret key to a key generation processor. The encryption processor computes ciphertexts, generates proofs, and produces final ciphertexts. The key generation processor receives the master secret key and a randomized function, samples a PRF key, generates an obfuscated program, and transmits a function key to a decryption processor. The decryption processor receives the function key and ciphertexts, calculates a decryption result, and electronically stores the result.

The present disclosure provides a method for secure message encryption and decryption using witness encryption. The method includes generating a master public key and a master secret key, generating common reference strings for a non-interactive zero-knowledge (NIZK) proof system and a commitment scheme, creating commitments using random values, and setting the master public and secret keys. A function key is generated by creating a dummy function tag and a NIZK proof. Message encryption involves generating a dummy input tag and creating a witness encryption ciphertext. The encrypted output includes attributes, the dummy input tag, and the witness encryption ciphertext. Decryption is performed using the function key and a witness decryption algorithm. The method enables secure message transmission with confidentiality and integrity throughout the encryption and decryption phases.

The disclosure relates to generating a ciphertext of arbitrary and flexibly large size and ensures that an adversary learns little about the encrypted data, even if the decryption key later leaks, unless substantially the entire ciphertext is stored. Given that communication will be inconveniently large for the adversary to store, the incompressible ciphertexts and signatures can be sent and received with low storage requirements for the honest users. In such a setting, the honest users would not store the entire ciphertext or signature, but instead generate, send, and process the communication bit-by-bit in a streaming fashion.

The invention relates to systems, methods, network devices, and machine-readable media for encrypting and decrypting messages in a decentralized multi-authority attribute-based encryption (MA-ABE) scheme that is provably fully-adaptively secure, specifically, secure against an attacker that may corrupt some of the authorities as well as perform key queries adaptively throughout the lifetime of the system.

A decentralized multi-authority attribute-based inner-product functional encryption FE (MA-ABIPFE) scheme in the prime-order bilinear groups under target-group-based assumptions is used for encryption. In some embodiments, any party can become an authority and there is no requirement for any global coordination other than the creation of an initial set of common reference parameters.

The invention relates to systems, methods, network devices, and machine-readable media for encrypting and decrypting messages in a decentralized multi-authority attribute-based encryption (MA-ABE) scheme for access structures described by monotone LSSS under the decisional bilinear Diffie-Hellman assumptions. The construction can also be modified to obtain an MA-ABE scheme under computational bilinear Diffie-Hellman assumptions.

Disclosed is an adaptively secure multiparty non-interactive key exchange (NIKE) from polynomially hard indistinguishability obfuscation and other standard assumptions. This improves on all prior such protocols, which required sub-exponential hardness. Several compilers are established which simplify the task of constructing new multiparty NIKE protocols, and also establish a close connection with a particular type of constrained PRF.

A public key cryptosystem has enhanced security based on the use of an augmented random oracle model (AROM). The system includes corresponding encryption and decryption functionality.

The invention relates to systems, methods, network devices, and machine-readable media for improved constructions of public-key functional encryption schemes for quadratic functions. In particular, the present disclosure relates to a new functional encryption scheme to compute quadratic functions so that the data owner controls what can be computed but is not involved in the calculation, and generates a decryption key which allows one to learn a quadratic function evaluation of some encrypted data.