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Source

Vinod Vaikuntanathan, the 'V' in [GVW14], talks about homomorphic trapdoor functions in his presentation talk Lattices and Cryptography: A Match Made in Heaven at PQCrypto 2014. HTDFs start at 23:32. The embedded video starts there, but you may want to rewind to the beginning to watch the entire, very inspiring, talk:

Literature

• [GVW14] Sergey Gorbunov, Vinod Vaikuntanathan, Daniel Wichs: Leveled Fully Homomorphic Signatures from Standard Lattices. In: STOC'15, Proceedings of the forty-seventh annual ACM symposium on Theory of computing. Portland, Oregon, June 14 - 17, 2015. Pages 469-477. (acm.org paywalled, full pdf an mit.edu, full pdf at iacr.org 2014/897)