Tag: RFC 4262

The "S/MIME Capabilities" certificate extension

When S/MIME certificates are issued, they usually contain a certificate extension "S/MIME Capabilities". This certificate extension is specified in RFC 4262 and can be used by compatible e-mail programs to specify the symmetric algorithms supported by the recipient of an encrypted message. The sender should then choose the strongest algorithm supported by the recipient.

Among others, Microsoft Outlook evaluates the extension and uses it to determine the symmetric algorithm for an encrypted email.

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Extend the "S/MIME Capabilities" certificate extension in issued certificates to include the Cryptography Next Generation (CNG) algorithms

When S/MIME certificates are issued, they usually contain a certificate extension "S/MIME Capabilities". This certificate extension is specified in RFC 4262 and can be used by compatible e-mail programs to specify the symmetric algorithms supported by the recipient of an encrypted message. The sender should then choose the strongest algorithm supported by the recipient.

However, if you take a look at the symmetric algorithms included in such a certificate, you will probably find that the list contains rather outdated algorithms - the "strongest" of these algorithms is Triple DES (3DES), which is now considered obsolete.

Continue reading "Extend the "S/MIME Capabilities" certificate extension in issued certificates to include the Cryptography Next Generation (CNG) algorithms"