Enable strong RSA key requirement (breaks Hyper-V VMs)
- Windows onlyThis script improves your privacy on Windows
- Single actionThis page belongs to a script, containing basic changes to achieve a task.
- Impact: Medium
System Functionality / Data Loss Risk: Moderate
This action improves privacy with minimal impact when you run the recommended script.
This action improves privacy with some impact when you run the recommended script. - Batch (batchfile)These changes use Windows system commands to update your settings.
- Administrator rights requiredThis script requires privilege access to do the system changes
- Fully reversible
You can fully restore this action (revert back to the original behavior) using this website.
The restore/revert methods provided here can help you fix issues.
Overview
This script improves your security by enforcing a minimum of 2048 bits for RSA encryption keys (PKCS
1 2).
RSA encryption keys play a crucial role in securing communications over the internet.
The Public-Key Cryptography Standards (PKCS) define how to use RSA keys for secure communication encryption.
Using keys that are too weak can expose your data to unauthorized access.
This script only affects the SSL/TLS handshake process. The SSL/TLS handshake is a key part of establishing a secure connection over the internet. By disabling this weak algorithm, the script improves the security of the connection.
From Windows 10, version 1507, and Windows Server 2016 onwards, the default RSA key size is 1024 bits 2. However, this script raises the client-side minimum to 2048 bits, aligning with modern security standards. Server-side RSA key strength relies on the server certificate 2.
Since 2013, internet standards and regulatory bodies have banned 1024-bit RSA keys due to security vulnerabilities 3. These entities, including the Federal Office for Information Security (BSI) in Germany 2 and the National Institute of Standards and Technology (NIST) in the USA 4 5, now recommend the use of keys that are 2048 bits or longer. RSA key exchanges of 2048 bits or are widely accepted.
In 2012, Microsoft deprecated 1024-bit RSA keys for their applications 5 6 and will end support for them in Windows by March 2024 3.
While 2048-bit keys balances security with efficiency 7, a shift towards stronger 4096-bit RSA keys is emerging. Projects like Debian 8, Fedora 9, and CaCert.org 10 use larger keys for long-term tasks.
However, this script disrupts connections to Hyper-V virtual machines, which still require 1024-bit keys 11. It does not affect other virtual environments such as Docker, WSL, or Windows Sandbox 11.
- The script prevents access to Hyper-V VMs.
- Using bigger keys increases security but may not work with some old or less secure apps.
- This can make your device slower and drain the battery faster.
This script is only recommended if you understand its implications.
Some non-critical or features may no longer function correctly after running this script.
This script can be fully reversed to restore changes if something goes wrong.
Sources
- Transport Layer Security (TLS) registry settings. Microsoft Learn. learn.microsoft.com. (2024).
Original: https://learn.microsoft.com/en-us/windows-server/security/tls/tls-registry-settings
Archived: https://web.archive.org/web/20240403064025/https://learn.microsoft.com/en-us/windows-server/security/tls/tls-registry-settings?tabs=rsa - Hilfsmittel zur Umsetzung von Anforderungen des IT Grundschutzes für Windows 10. Bundesamt für Sicherheit in der Informationstechnik. bsi.bund.de. (2024).
Original: https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Grundschutz/Hilfsmittel/Hilfsmittel_Anforderungen_des_IT_Grundschutzes_fuer_Windows_10.pdf
Archived: https://web.archive.org/web/20240402183249/https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Grundschutz/Hilfsmittel/Hilfsmittel_Anforderungen_des_IT_Grundschutzes_fuer_Windows_10.pdf?__blob=publicationFile&v=2 - Deprecated features in the Windows client - What's new in Windows. Microsoft Learn. learn.microsoft.com. (2024).
Original: https://learn.microsoft.com/en-us/windows/whats-new/deprecated-features
Archived: https://web.archive.org/web/20240403064138/https://learn.microsoft.com/en-us/windows/whats-new/deprecated-features - NIST Special Publication 800-131A Revision 2. Transitioning the Use of Cryptographic Algorithms and Key Lengths. nvlpubs.nist.gov. (2024).
Original: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-131Ar2.pdf
Archived: https://web.archive.org/web/20240402105205/https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-131Ar2.pdf - request by bricedobson. undergroundwires/privacy.sexy. GitHub.com. (2024).
Original: https://github.com/undergroundwires/privacy.sexy/pull/165
Archived: https://web.archive.org/web/20240403064107/https://github.com/undergroundwires/privacy.sexy/pull/165 - RSA keys under 1024 bits are blocked - Microsoft Community Hub. techcommunity.microsoft.com. (2024).
Original: https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/rsa-keys-under-1024-bits-are-blocked/ba-p/1128997
Archived: https://web.archive.org/web/20240403064204/https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/rsa-keys-under-1024-bits-are-blocked/ba-p/1128997 - RSA Key Sizes: 2048 or 4096 bits?. danielpocock.com. (2024).
Original: https://danielpocock.com/rsa-key-sizes-2048-or-4096-bits
Archived: https://web.archive.org/web/20240402113046/https://danielpocock.com/rsa-key-sizes-2048-or-4096-bits/ - Keysigning - Debian Wiki. wiki.debian.org. (2024).
Original: https://wiki.debian.org/Keysigning
Archived: https://web.archive.org/web/20240402105239/https://wiki.debian.org/Keysigning#Step_1:_Create_a_RSA_keypair - Fedora keeps you safe. The Fedora Project. fedoraproject.org. (2024).
Original: https://fedoraproject.org/security
Archived: https://web.archive.org/web/20240402105244/https://fedoraproject.org/security/ - Certification Practice Statement (CPS). cacert.org. (2024).
Original: http://www.cacert.org/policy/CertificationPracticeStatement.html
Archived: https://web.archive.org/web/20240402112840/http://www.cacert.org/policy/CertificationPracticeStatement.html#p6.1.5 - github.com. (2024).
Original: https://github.com/undergroundwires/privacy.sexy/issues/363
Archived: https://web.archive.org/web/20240519131322/https://github.com/undergroundwires/privacy.sexy/issues/363
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:: Require "PKCS" key exchange algorithm to have at "2048" least bits keys for TLS/SSL connections
:: Set the registry value: "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS!ServerMinKeyBitLength"
PowerShell -ExecutionPolicy Unrestricted -Command "$registryPath = 'HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS'; $data = '2048'; reg add 'HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS' /v 'ServerMinKeyBitLength' /t 'REG_DWORD' /d "^""$data"^"" /f"
:: Set the registry value: "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS!ClientMinKeyBitLength"
PowerShell -ExecutionPolicy Unrestricted -Command "$registryPath = 'HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS'; $data = '2048'; reg add 'HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\PKCS' /v 'ClientMinKeyBitLength' /t 'REG_DWORD' /d "^""$data"^"" /f"
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Paste the commands into Command Prompt and press Enter to run.Some changes require a system restart to take effect
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