CPA-secure SKE ⇒ SKE

Fully-black-box reduction · standard model · folklore · security loss: none

Statement

A CPA-secure symmetric-key encryption scheme, with the same algorithms, is a symmetric-key encryption scheme: the weaker notion only drops security guarantees — folklore.

Notes

• The converse fails: the one-time pad is a symmetric-key encryption scheme with perfect one-time security but not CPA-secure, which is why SKE ⇒ OWF takes CPA security as its hypothesis — standard.