What is a .p7m or .p7s File?

“.p7m” and “.p7s” files are both related to PKCS #7 (Public Key Cryptography Standards #7) and are used for secure email and digital signatures. These files encapsulate data with cryptographic signatures and certificates to verify the identity of the sender and/or the integrity of the message.

1. “.p7m” File (Signed and Encrypted Content)

• Description: A “.p7m” file is a digitally signed and/or encrypted file, typically created as part of a Secure/Multipurpose Internet Mail Extensions (S/MIME) email.
• Content: The “.p7m” file usually contains the original message or document along with the digital signature and, optionally, encryption.
• Usage: Commonly seen in secure email, such as encrypted or signed email attachments.
• Opening: To open a “.p7m” file, you’ll typically need an email client or application that supports S/MIME (e.g., Microsoft Outlook, Apple Mail). You may also need access to the correct decryption key or certificates if the file is encrypted.

2. “.p7s” File (Detached Signature File)

• Description: A “.p7s” file is a detached signature file that accompanies a message or document to verify its integrity and authenticity.
• Content: It contains the digital signature but not the actual content of the message or document. Instead, it references the original content externally.
• Usage: Often attached to signed emails or documents as proof of authenticity, with the email body or document being the primary content.
• Opening: Like “.p7m” files, “.p7s” files can typically be opened with S/MIME-compatible email clients or applications that can verify digital signatures, like Microsoft Outlook or Apple Mail.

Summary of Differences:

• “.p7m” files include both the content and signature (and potentially encryption).
• “.p7s” files include only the detached digital signature, referencing the original content separately.

These file types are commonly used in secure communications to ensure data integrity, authenticity, and privacy.