To encrypt & decrypt files use these commands:

OpenSSL

To encrypt:

openssl enc -in inputfilename -out outputfilename -aes256

To decrypt:

openssl enc -in encryptedfile -out outputfilename -aes256 -d

GPG

Encrypt only using the public key of user@example.com (only that user can decrypt this file)

gpg -er user@example.com -o outputfile.enc inputfile

Encrypt and sign:

gpg -u you@example.com -ser user@example.com -o outputfile.enc inputfile

To decrypt:

gpg -do outputfilename encryptedfilesname