Install by hand, without the installer

Windows

1. Double-click the downloaded russian_trusted_root_ca.cer and click Install Certificate…
2. Choose Local Machine (needs administrator rights) or Current User if you have none. Click Next.
3. Choose Place all certificates in the following store → Browse… → Trusted Root Certification Authorities → OK → Next → Finish.
4. If Windows shows a security warning naming “Russian Trusted Root CA”, click Yes.
5. Close the browser completely and open it again.

Check In the certificate window, on the Details tab, the Thumbprint must be: 8ff915ccab7bc16f8c5c8099d53e0e115b3aec2f

Intermediates install the same way into Intermediate Certification Authorities. To remove: Win+R → certlm.msc (or certmgr.msc for the current user) → Trusted Root Certification Authorities → Certificates.

macOS

1. Double-click the downloaded russian_trusted_root_ca.cer — Keychain Access opens. If it asks where to add it, choose System and enter your password.
2. In Keychain Access select the System keychain, the Certificates tab, find Russian Trusted Root CA and double-click it.
3. Expand Trust and set “When using this certificate” to Always Trust.
4. Close the window, enter the administrator password and restart the browser.

Check In the certificate window, under Fingerprints, SHA-256 must be: D2 6D 2D 02 31 B7 C3 9F 92 CC 73 85 12 BA 54 10 35 19 E4 40 5D 68 B5 BD 70 3E 97 88 CA 8E CF 31

To remove: Keychain Access → System → right-click the certificate → Delete.

Linux

Open a terminal in the folder with the downloaded file and run the commands for your distribution.

sudo cp russian_trusted_root_ca.cer /usr/local/share/ca-certificates/russian_trusted_root_ca.crt
sudo update-ca-certificates

sudo cp russian_trusted_root_ca.cer /etc/pki/ca-trust/source/anchors/
sudo update-ca-trust

sudo trust anchor --store russian_trusted_root_ca.cer

sudo cp russian_trusted_root_ca.cer /etc/pki/trust/anchors/
sudo update-ca-certificates

Check the file The command sha256sum russian_trusted_root_ca.cer must print: 936a43fea6e8e525bcc0f81acd9c3d21b4fc4b9b68acea7906d698005afc6504

Chrome and Firefox on Linux keep their own stores. For Chrome and Chromium: certutil -d sql:$HOME/.pki/nssdb -A -t "C,," -n "Russian Trusted Root CA" -i russian_trusted_root_ca.cer (package libnss3-tools or nss-tools). In Firefox: Settings → Privacy & Security → Certificates → View Certificates → Authorities → Import, then tick “Trust this CA to identify websites”.