Question:

What is the purpose and function of the winscp.rnd file that WinSCP creates in the appdata roaming folder? Is it safe to delete this file without affecting the performance or security of WinSCP?.

Answer:

What is the winscp.rnd file and can you delete it?

WinSCP is a popular file manager for Windows that supports various protocols such as FTP, SFTP, S3 and WebDAV. It allows users to transfer files between local and remote computers securely and efficiently. WinSCP has many features and options that can be customized by the user, including the ability to use it as a portable application.

One of the files that WinSCP creates and uses is the winscp.rnd file. This file is a random seed file that WinSCP uses to generate random numbers for encryption and authentication purposes. Random numbers are essential for ensuring the security and privacy of the data that is transferred using WinSCP. The winscp.rnd file stores some bits of randomness that WinSCP collects from various sources, such as mouse movements, keyboard inputs, system time, etc. WinSCP updates the winscp.rnd file every time it runs and uses it as a source of entropy for the next session.

Where is the winscp.rnd file located?

By default, WinSCP stores the winscp.rnd file in the C:\\Users\\username folder, where username is the name of the current user. However, this location can be changed by the user in the preferences. For example, if the user wants to use WinSCP as a portable application, they can configure WinSCP to store the winscp.rnd file in the same folder as the WinSCP executable, or in a subfolder, or in a different folder altogether. To change the location of the winscp.rnd file, the user needs to edit the RandomSeedFile parameter in the [Configuration\\Interface] section of the winscp.ini file, or use the graphical interface in the Preferences dialog.

Can you delete the winscp.rnd file?

The short answer is yes, you can delete the winscp.rnd file without affecting the performance or security of WinSCP. However, there are some consequences and trade-offs that you should be aware of before doing so.

The main consequence of deleting the winscp.rnd file is that WinSCP will have to generate a new one the next time it runs. This means that WinSCP will have to collect enough randomness from the system and the user to create a sufficiently random seed file. This process may take some time and may require some user interaction, such as moving the mouse or pressing some keys. Depending on the speed and entropy of the system, this process may be fast and unnoticeable, or it may be slow and annoying.

The main trade-off of deleting the winscp.rnd file is that WinSCP will have to start from scratch every time it runs, instead of using the previous randomness that was stored in the file. This may reduce the quality and security of the random numbers that WinSCP generates, especially if the system or the user does not provide enough entropy. This may make WinSCP more vulnerable to attacks that try to guess or predict the random numbers that WinSCP uses for encryption and authentication.

Therefore, deleting the winscp.rnd file is not recommended, unless you have a good reason to do so. For example, you may want to delete the winscp.rnd file if you are concerned about the privacy of the randomness that is stored in the file, or if you want to free up some disk space, or if you want to reset the randomness of WinSCP for some reason. However, in most cases, it is better to leave the winscp.rnd file alone, or to change its location to a more convenient or secure place.

Conclusion

The winscp.rnd file is a random seed file that WinSCP uses to generate random numbers for encryption and authentication purposes. It is stored by default in the C:\\Users\\username folder, but it can be changed by the user in the preferences. Deleting the winscp.rnd file is possible, but it has some consequences and trade-offs that may affect the performance and security of WinSCP. Therefore, it is advisable to keep the winscp.rnd file, or to move it to a different location, unless you have a good reason to delete it.