PKCS 7

In cryptography, PKCS #7 ("PKCS #7: Cryptographic Message Syntax", "CMS") is a standard syntax for storing signed and/or encrypted data.

PKCS #7 is one of the family of standards called Public-Key Cryptography Standards (PKCS) created by RSA Laboratories.

Windows uses the .p7b file name extension[6] for both these encodings.

A typical use of a PKCS #7 file would be to store certificates and/or certificate revocation lists (CRL).

Here's an example of how to first download a certificate, then wrap it inside a PKCS #7 archive and then read from that archive: