Let $I$ be a countable index set. An ensemble indexed by $I$ is a sequence of random variables indexed by $I$. Namely, $X\; =\; \backslash \{X\_i\backslash \}\_\{i\; \backslash in\; I\}$, where the $X\_i$'s are random variables, is an ensemble indexed by $I$.

References

• Goldreich, Oded (2001). Foundations of Cryptography: Volume 1, Basic Tools. Cambridge University Press. ISBN 0-521-79172-3. Fragments available at the author's web site.

Algorithmic information theory | Cryptography