rspec/rules/S2278/description.adoc

According to the US National Institute of Standards and Technology (NIST), the Data Encryption Standard (DES) is no longer considered secure:
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Adopted in 1977 for federal agencies to use in protecting sensitive, unclassified information, the DES is being withdrawn because it no longer provides the security that is needed to protect federal government information.
Federal agencies are encouraged to use the Advanced Encryption Standard, a faster and stronger algorithm approved as FIPS 197 in 2001.
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For similar reasons, RC2 should also be avoided.