The National Institute of Standards and Technology (NIST) announces a workshop to discuss modes of operation for the protection of data using a symmetric key block cipher algorithm. The results of this workshop will be used by NIST in development a draft modes of operation standard for symmetric key block cipher algorithms. Comments and papers are encouraged prior to the workshop to propose, define, and justify any modes that are appropriate for NIST to include in such a standard. These comments and papers should be addressed to EncryptionModes@nist.gov.