Homomorphic Encryption
Definition
Homomorphic encryption enables certain computations on encrypted data without revealing it in plaintext beforehand.
Depending on the method, limited or very general operations are supported. The result remains encrypted and can subsequently be decrypted with the appropriate key.
Simply explained
How to perform calculations with numbers in sealed envelopes without seeing the numbers during processing.
Why it matters in practice
Relevant for particularly sensitive data processing across trust boundaries, but often involves significant computational and implementation effort.
Example from business
A company is examining whether statistical analyses on encrypted sensitive data are possible at an external computing service.
Limits and pitfalls
- Underestimating performance effort; considering FHE as a replacement for all other security measures; ignoring threat models and key management.
Origin & history
Craig Gentry presented a fully homomorphic construction based on ideal lattices in 2009.
Use in mid-sized companies
- Possible application: specialized privacy-friendly analysis when plaintext processing at the service provider is to be avoided.
Frequently asked questions
Can arbitrary software be executed unchanged on FHE?
In practice, usually no; procedures and computations must be adapted. Is FHE free in terms of computation time? No.
Sources
- Fully Homomorphic Encryption Using Ideal Lattices · Gentry (2009), Fully Homomorphic Encryption Using Ideal Lattices
- Microsoft SEAL · Microsoft SEAL
- Dissertation und Veröffentlichungen · Gentry, Dissertation und Veröffentlichungen
Source verification: 10./11.10.2026.
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