PGP keys

Hi Experts,

1. I am sending a file from FTP1 to FTP2, see picture below, the file needs to be PGP encrypted as below, I am just wondering where should I put both Public and Private key, in FTP1, or PI or FTP2?

2. Also when I am receiving a file from FTP2 to FTP1, see picture below, the file needs to be PGP encrypted as below, I am just wondering where should I put both Public and Private key, in FTP1, or PI or FTP2?

Thank you for your advices.

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