I setup a GPG encryption transfer with a 3rd party to transfer XML files.
On decrypting the GPG XML file I noticed when I vi’d the file I had ï»¿ at the beginning of the file – everything else in the file was displayed OK.
In the end it turned out it was all to do with character sets – the default AIX charcter set is ISO8859-1 and the file was sent from a server that was using UTF-8
The ï»¿ I was seeing is the BOM Byte Order Mark – Wikipedia has a useful page that shows what characters are displayed on a ISO8859-1 system for the various UTF encodings.
To convert to ISO8859-1 you can use iconv