Hexdump Privileged File Read
Read with Hexdump
sudo -u user.name /usr/bin/hexdump -v -e '/1 "%02x"' /home/user.name/.ssh/id_rsa > hex.dump-v -e '/1 "%02x"' syntax tells hexdump to read byte-per-byte and output in lowercase hexadecimal, whereas hexdump may not preserve the original byte order of the file (or mask duplicates with a *), leading to scrambling of data.
Restore Original
Note: If the file is a standard hexdump and not a byte-per-byte read, use xxd -r without the -p flag.
The easiest way to identify this is if there are leading offsets such as 00000000 and so on.
xxd -r -p hex.dump > id_rsaConvert from hexdump hexadecimal output back to original file encoding (probably UTF-8)