I cannot generate SHA-2 Key with old, SourceTree-affiliated version of puTTY gen

[Brad Rosenheim]

I am using Windows 11 with SourceTree v. 3.4.7 on a Microsoft Surface 7.

I have not been able to push to Github from SourceTree or from Git Bash. When I try from SourceTree, I get the following error: ERROR: You're using an RSA key with SHA-1, which is no longer allowed. Please use a newer client or a different key type.
Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.

The link explains that Github, as of today (Jan. 11, 2022) no longer allows SHA-1 keys. It has to be SHA-2 or higher. The link above contains the passage:

"

Clients relying on older SSH implementations will need to be updated. (The standard Git client uses your operating system’s SSH implementation on Linux and macOS.) Common examples include:

• OpenSSH before version 7.2
• PuTTY before 0.75

GitHub has worked with these vendors to make new versions of their packages available.

"

However, no matter what I do, I cannot get SourceTree to interface with anything but puTTY gen version 0.70.2. I can download puTTY gen version 0.75, but it will not interface with SourceTree. I can generate a key using the external version of puTTY gen, but it is not ideal (I run a lab with students of various backgrounds, and github is difficult enough for them without the added requirements of maintaining a SSH generator that is not affiliated with SourceTree).

Will SourceTree start supporting later versions of puTTY, or should I look for another "friendly" way to authenticate for Git pushes and pulls?

[Jonathan Vigh]

SourceTree v3.4.9 uses puTTy 0.76. I was able generate an ecdsa key following a procedure similar to this:
https://confluence.atlassian.com/sourcetreekb/generate-and-load-ssh-keys-into-sourcetree-with-putty-790629663.html

Then I was able to upload this key to GitHub. I ran into other headaches and found the following resources helpful:
https://community.atlassian.com/t5/Sourcetree-questions/Credential-selector-helper/qaq-p/1353371
https://kevinfiol.com/blog/getting-rid-of-the-credential-helper-selector-on-git-for-windows/
https://community.atlassian.com/t5/Sourcetree-questions/CredentialHelperSelector/qaq-p/1334704
https://github.com/microsoft/Git-Credential-Manager-for-Windows/releases

For some reason, Git didn't install when I first installed SourceTree. the Git Credential Manager for Windows will install that for you. After following all of these steps, it began working for me. Best of luck!