Apache Nifi SOCKS Proxy Setup

I try to access a SFTP Source with Apache Nifi. The processor does not contain proxy settings. Therefor I wanted to provide Proxy Details on Startup as JVM Parameters.

java.arg.16=-DsocksProxyHost="123.123.123.123"
java.arg.17=-DsocksProxyVersion=5
java.arg.18=-Djava.net.socks.username="MYUSERNAME"
java.arg.19=-Djava.net.socks.password="MYPASSWORD"
java.arg.20=-DsocksProxyPort=1080

This does not work. I could not find any implementation of jsch explicitly using a proxy in the nifi code on github
https://github.com/apache/nifi/search?utf8=%E2%9C%93&q=jsch&type=

The question is:
Is Jsch using the provide parameters internally?