# Distribution ensemble

In cryptography, a distribution ensemble or probability ensemble is a family of distributions or random variables $X = \{X_i\}_{i \in I}$ where $I$ is a (countable) index set, and each $X_i$ is a random variable, or probability distribution. Often $I=\N$ and it is required that each $X_n$ have a certain property for n sufficiently large.
A uniform ensemble $U = \{U_n\}_{n \in \mathbb{N}}$ is a distribution ensemble, uniformly distributed over strings of length n.