# Key Encapsulation Mechanism

(Redirected from KEM)

Key Encapsulation Mechanism, also known as KEM, is a triple of algorithms ${\displaystyle {\mathcal {K}}=\{{\text{KeyGen}},{\text{Encaps}},{\text{Decaps}}\}}$ and a corresponding key space ${\displaystyle K}$, a ciphertext space ${\displaystyle {\text{C}}}$ with

1. The ${\displaystyle {\text{KeyGen}}(n)}$ algorithm takes a public parameter ${\displaystyle n}$ as an input and returns a public and secret-key pair (${\displaystyle {\text{pk}},{\text{sk}}}$).
2. The probabilistic ${\displaystyle {\text{Encaps}}(pk)}$ (encapsulation) algorithms takes ${\displaystyle {\text{pk}}}$ as an input and returns a ciphertext ${\displaystyle c\in C}$ and a key ${\displaystyle k\in K}$.
3. The deterministic ${\displaystyle {\text{Decaps}}(sk,c)}$ (decapsulation) algorithm takes ${\displaystyle {\text{sk}},{\text{c}}}$ as inputs and returns a key ${\displaystyle k\in K\cup \{\perp \}}$, with ${\displaystyle \perp }$ denoting as a failure.