Proceedings of the 20th International Conference on Security and Cryptography,SECRYPT 2023, Rome, Italy, July 10-12, 2023
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
We introduce the notion of oblivious secret sharing as an enhancement of (conventional) secret sharing with the added possibility of (plausibly) denying that some shares even exist. Secret sharing is a cryptographic technique that allows a distributed secure storage of information across multiple parties, such that no party or pre-defined coalition of parties can reconstruct the stored secret. Confidentiality, in this regard, does only apply to the secret, but not the shares themselves. Oblivious secret sharing extends the secrecy also to the shares, thereby adding the additional possibility of denying the existence of shares in first place, or to reconstruct a different, harmless, secret upon force. We investigate a combination of steganography and secret sharing to enhance both primitives at the same time: secret sharing adds deniability to steganography and steganography adds extended confidentiality to secret sharing. Our construction is generic in its use of steganography, but concrete in the used secret sharing scheme. The latter is a form of multisecret sharing, letting us secretly hide a set of messages in a larger collection of images, such that the secrets are, in a steganographic way, hidden, but disclosure upon force can be made with plausible deniability. This deniability even extends to the number of secrets embedded in the picture collection. This number is as well deniable. We corroborate our construction by providing an implementation in a Jupyter notebook
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