pen

pen is a lightweight alternatve to PGP for securely encrypting files; it uses the Argon2 algorithm for key-stretching passwords and NaCl's secretbox for data encryption. If a filename ends in .pen, it will be decrypted rather than encrypted. Upon successful encryption or decryption, the original file or .pen file, respectively, is securely removed using shred from GNU coreutils. If shred is not available, the original file remains untouched.

usage: pen [-h, -v] file [files...]
Options are:
  -h, --help      display this help and exit
  -v, --version   output version information and exit

release binaries

are available here for amd64/all major OSes

for unixes

make && make install

everybody else

go build

note

Shredding the original input may still be insecure due to the underlying charactersitics of your filesystem. In contexts requiring extremely robust security, it may be best to consider another option and/or to consult a professional.