CA/Browser Forum

S/MIME Baseline Requirements (S/MIME BR)

Baseline Requirements for the Issuance and Management of Publicly-Trusted S/MIME Certificates

Draft Version (undergoing IPR Review)

N/A

Current Version

S/MIME Baseline Requirements v. 1.0.15 (redline) - adopted by Ballot SMC017v2

Previous Versions

S/MIME Baseline Requirements v. 1.0.14 (redline) - adopted by Ballot SMC016

S/MIME Baseline Requirements v. 1.0.13 (redline) - adopted by Ballot SMC015v2

S/MIME Baseline Requirements v. 1.0.12 (redline) - adopted by Ballot SMC014

S/MIME Baseline Requirements v. 1.0.11 (redline) - adopted by Ballot SMC013

S/MIME Baseline Requirements v. 1.0.10 (redlined) – adopted by Ballot SMC012

S/MIME Baseline Requirements v. 1.0.9 (redlined) – adopted by Ballot SMC011

S/MIME Baseline Requirements v. 1.0.8 (redlined) – adopted by Ballot SMC010

S/MIME Baseline Requirements v. 1.0.7 (redlined) – adopted by Ballot SMC09

S/MIME Baseline Requirements v. 1.0.6 – adopted by Ballot SMC08

S/MIME Baseline Requirements v. 1.0.5 – adopted by Ballot SMC07

S/MIME Baseline Requirements v. 1.0.4 – adopted by Ballot SMC06

S/MIME Baseline Requirements v. 1.0.3 – adopted by Ballot SMC05

S/MIME Baseline Requirements v. 1.0.2 – adopted by Ballot SMC04

S/MIME Baseline Requirements v. 1.0.1 – adopted by Ballot SMC03

S/MIME Baseline Requirements v1.0.0 – adopted by Ballot SMC01

Latest releases
Server Certificate Requirements
SC098: Process RFC 8657 CAA Parameters - Jun 16, 2026

Code Signing Requirements
v3.8 - Aug 5, 2024

What’s Changed CSC-25: Import EV Guidelines to CS Baseline Requirements by @dzacharo in https://github.com/cabforum/code-signing/pull/38 Full Changelog: https://github.com/cabforum/code-signing/compare/v3.7...v3.8

S/MIME Requirements
v1.0.15 - Ballot SMC017v2 - Jul 30, 2026

This ballot increases the minimum RSA key size for Root and Subordinate CA certificates in the S/MIME BRs from 2048 to 4096 bits for keys created after September 15, 2026, while retaining the 2048-bit minimum for Subscriber certificates. The ballot further requires that by September 15, 2027, CAs SHALL NOT issue Subscriber certificates from any Sub-CA whose RSA key modulus is less than 3072 bits, effectively sunsetting issuance from legacy 2048-bit Sub-CAs. The ballot also includes minor typographic corrections. This ballot is proposed by Martijn Katerbarg (Sectigo) and endorsed by Ben Wilson (Mozilla) and Stephen Davidson (DigiCert)

Network and Certificate System Security Requirements
Version 2.0.5 (Ballot NS-008) - Jul 9, 2025

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The Certification Authority Browser Forum (CA/Browser Forum) is a voluntary gathering of Certificate Issuers and suppliers of Internet browser software and other applications that use certificates (Certificate Consumers).