Tata Consultancy Services Limited

Arinjita Paul

Rajan Mindigal Alasingara Bhattachar

Imtiyazuddin Shaik

Meena Singh Dilip Thakur

Habeeb Basha Syed

Rajan Mindigalalasingara Bhattachar

Rajan Mindigal Bhattachar

This disclosure relates generally to a method and system for re-encryption of an encrypted data. State-of-the-art methods provide the re-encryption scheme for a specific Fully Homomorphic Encryption (FHE) encrypted data. However, a generic scheme that converts any given FHE scheme to an HPRE scheme is not yet achieved. The disclosed method provides re-encryption of the encrypted data transferred between a first user and a second user by a re-encryption key. The re-encryption key is obtained by splitting a private key of the first user into a primary private key and a secondary private key. The primary private key generates a public re-key component using probabilistic encryption algorithm; and the secondary private key generates a private re-key component using probabilistic switch key generation algorithm. Both the private re-key and the public re-key are consolidated further to generate the re-encryption key.

Method and system for re-encryption of encrypted data by generating re-encryption key

The present disclosure a method for a lattice-based homomorphic proxy re-encryption scheme. Conventional methods are attribute based and the attribute-based encryption schemes employ very expensive operations and generate long ciphertexts and secret keys (whose sizes also increase linearly with the size of the access policy), which makes them hard to implement in real-life applications. The present disclosure provides a unidirectional, single-hop HPRE scheme from the Learning With Errors (LWE) assumption which is Chosen Plaintext Attack (CPA) secure. Further, the present disclosure is based on the widely accepted BGV algorithm that supports both levelled FHE operations as well as arbitrary number of ciphertexts with unique and secure re-encryption key generation. Further, the present disclosure provides batch evaluation of ciphertexts, in order to enable re-encryption and evaluation of multiple ciphertexts.

Method and system for a lattice-based homomorphic proxy re-encryption scheme

This disclosure relates to field of cryptography and digital signatures. The constant theft of cryptocurrencies is due to compromise of the secret signing key inherently stored in a single location. Also, one of challenges in the existing ECDSA signature is single point failure, wherein the signing key (private key) is prone to theft. The disclosed technique overcomes the challenging in the existing techniques by party distributed signature that ensures the safety of the private key. The disclosed techniques slits the key in two parts and saves at two different locations/machines. Further based on a ECDSA based technique, the digital signature is obtained securely using several steps that includes generation of first two parts of digital signature at one party, generation of the second two parts of digital signature at second party, finally decrypting a complete digital signature at the first party.

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Thane, India

Arinjita Paul