# EvalAutomorphismKeyGen ModInverse index

**URL:** <https://openfhe.discourse.group/t/evalautomorphismkeygen-modinverse-index/1801>\
**Category:** Library Questions\
**Created:** [December 23, 2024, 5:41am UTC](https://openfhe.discourse.group/t/evalautomorphismkeygen-modinverse-index/1801 "2024-12-23T05:41:22Z")\
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**Author:** ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)\
**Post date:** [December 23, 2024, 10:26pm UTC](https://openfhe.discourse.group/t/evalautomorphismkeygen-modinverse-index/1801/2 "2024-12-23T22:26:45Z")

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The double-hoisting optimization from [Efficient Bootstrapping for Approximate Homomorphic Encryption with Non-Sparse Keys](https://eprint.iacr.org/2020/1203) is used here (See Section 4.2 of the paper). It has no effect on efficiency for a single automorphism but is more efficient when multiple automorphisms for the same ciphertext are needed.

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