In a public-key cryptosystem each user has an associated public key with which other users can send them an encrypted message. The correspondence between the user's identity and their public key is verified using certificates which are issued by some trusted authority.

Identity-based encryption (IBE) offers an alternate approach where one only needs the identity of the recipient to send them an encrypted message. The recipient then uses a secret key associated only with their identity to decrypt the message.

Attribute-based encryption (ABE) is a modification of the IBE setting for a system where users have attributes associated to them and a data owner wishes to send encrypted messages to subsets of users based on their attributes.

The goal of this seminar is to build up from the idea of an IBE proposed by Shamir in [1] on to the first paper on ABE by Sahai and Waters [2]. From there, two classes of ABEs are studied, namely ciphertext policy [3] and key policy ABEs [4].

[1] Shamir, A. (1985). Identity-Based Cryptosystems and Signature Schemes. In: Blakley, G.R., Chaum, D. (eds) Advances in Cryptology. CRYPTO 1984. Lecture Notes in Computer Science, vol 196. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-39568-7_5

[2] Sahai, A., Waters, B. (2005). Fuzzy Identity-Based Encryption. In: Cramer, R. (eds) Advances in Cryptology – EUROCRYPT 2005. EUROCRYPT 2005. Lecture Notes in Computer Science, vol 3494. Springer, Berlin, Heidelberg. https://doi.org/10.1007/11426639_27

[3] J. Bethencourt, A. Sahai and B. Waters, "Ciphertext-Policy Attribute-Based Encryption," 2007 IEEE Symposium on Security and Privacy (SP '07), Berkeley, CA, USA, 2007, pp. 321-334, doi: 10.1109/SP.2007.11.

[4] Vipul Goyal, Omkant Pandey, Amit Sahai, and Brent Waters. 2006. Attribute-based encryption for fine-grained access control of encrypted data. In Proceedings of the 13th ACM conference on Computer and communications security (CCS '06). Association for Computing Machinery, New York, NY, USA, 89–98. https://doi.org/10.1145/1180405.1180418