NISTP | NISTP is part of my work for CS | Android library

I am attempting to scp a file onto a Synology NAS (into the /tmp directory). Doing this from the command line of my Ubuntu machine works as intended. Running the PHP code works as intended against a regular Linux distro (as in every distro I've tried - Ubuntu, Debian, Centos, Redhat, Suse, Arch). Even against other *nix it's fine (MacOS, AIX, etc). I don't think it's a PHPSecLib issue as such, but that's what we're using. Ubuntu 18.04 to Synology DS3615xs running DSM 6.1.7-15284. The credentials are correct. The user has write permission on /tmp. I have posted the full log (it's a test Synology that is unused). Any assistance would be most appreciated.

If I run the scp from the shell of my Ubuntu machine, I get the below logs and it works as intended.

I am trying to connect to an SFTP server using WinSCP and PowerShell and have hit the following snag

Error: SSH host key fingerprint "ssh-rsa 2048 ABCDE+I9v1+pLxkhZkod6yAbEh0o7a8wlSsI+ABCDEF" does not match pattern /((ssh-rsa|ssh-dss|ssh-ed25519|ecdsa-sha2-nistp(256|384|521))( |-))?(\d+ )?(([0-9a-f]{2}(:|-)){15}[0-9a-f]{2}|[0-9a-zA-Z+/]{43}=)(;((ssh-rsa|ssh-dss|ssh-ed25519|ecdsa-sha2-nistp(256|384|521))( |-))?(\d+ )?(([0-9a-f]{2}(:|-)){15}[0-a-f]{2}|[0-9a-zA-Z+/]{43}=))*/

The ABCDE and ABCDEF in the quoted string are just me obscuring the fingerprint.

I've checked the existing SO responses ( SSH host key fingerprint ... does not match pattern ... when using WinSCP .NET assembly in C# to download files, SSH host key fingerprint does not match pattern C# WinSCP) but they don't apply.

I have a vague knowledge of regular expressions, and it looks like it should match to me, so I hope I am missing something simple. I have the 'ssh-rsa', then a space ( |-), then a number of digits followed by space (\d+ ), then 43 characters that match [0-9a-zA-Z+/]{43} (it's the fact that I have a 43-character string that makes me thing I have a correct fingerprint and am just missing some syntactic trivia). The whole of the second half of the pattern is just a repeat of the first, and I'm assuming an optional one, so I don't know what's not being accepted?

I'm writing a C# app (want to eventually create a Windows service if I can get this working) to download files from a server using SCP (I am limited to SCP as the only option). I am using the WinSCP .NET assembly (v 5.15.3).

I have an SSH tunnel between my PC and the server, so the following works from the command line:

I'm trying simple copy files between server sftp using gaufrette and phpseclib. Local adapter server no problem sends more than 1GB. If i am trying send remote always stops at 1GB logs look like