how to get private key

[Afzal, Naeem M]

Hi

I have general question regarding private key security.
If a user creates its private public key pair by using some passphrase on a system. Can this pair be taken to a different system and decrypt files that were generated using its public key? My guess is no, but needed to confirm with you guys. If it is possible, then how it will be done, any command to list private key etc. Also how can we protect where no one can steel this private key from a system other than restricting users access to the system?

Thanks
naeem