Network Management

Changing SCP/SFTP Server SSH RSA key size from 1024 to 2048

This article explains how to resolve the issue if device backup fails due to the SCP/SFTP Server using a smaller SSH RSA key.

First published date

8/7/2020 4:32 AM

Last published date

8/14/2025 9:36 PM

Overview

Our SCP/SFTP Server, which is bundled with the SolarWinds Platform, is configured to use an SSH RSA key of size 1024 bits. However, we recently received reports from customers related to devices requiring longer keys (e.g., 2048 bits). For example, Cisco UCS now requires a key size of 2048 bits or more when configured in FIPS mode.

In this article you will find easy steps to increase the size of SSH RSA key size to meet devices' requirements.

Product section

Network Configuration Manager

Resolution

To change the SSH RSA key size, follow the steps below:

  1. Generate a new RSA key using your preferred tool.
    Example using the PuTTY Key Generator

    1. ​​​If you do not have PuTTY installed, download the PuTTY Key Generator using the link below.
      https://www.ssh.com/academy/ssh/putty/windows/puttygen#puttygen-download-and-install 

    2. Generate the key (default settings are SSH RSA and 2048 bits; you can adjust the size if you require a longer one).

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Note: Leave the Key passphrase blank.

  1. Export the generated key as an OpenSSH key and save it to C:\ProgramData\SolarWinds\sftp.rsa.

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  1. Restart SCP/SFTP Server.

REF: https://thwack.solarwinds.com/discussion/4747/sftp-scp-server-rsa-key-too-small