# README

pemaead

A simple PEM enveloppe using AES AEAD encryption mode go package/library.

Purpose

a simple io.ReadCloser / io.WriteCloser interface, to store and encrypt/tag a reasonnably small amount of data at rest, an attempt to be reasonnably resistant to offline attacks as well as ensure data + header integrity using an "encrypt-then-MAC" approach (thanks to AEAD and trying to avoid Encrypt-and-MAC and MAC-then-encrypt kind of schemes).

Relying on AEAD properties to ensure integrity of data + headers (+ CSRNG key derivation salt & AEAD nonce).

Key is derivated using strong derivation functions trying to slow down brute-force:

Scrypt
Argon2id
PBKDF2 (if standard is needed)

Using AES-GCM-256 encryption mode & Argon2id key derivation by default, a random salt & nonce.

Usage Examples

Important notes:

Write() is only buffering, the call to Close() will actually write your data, keep that in mind.
Close() will close the underlying fd provided to the Writer.

Writer

...
fd, err := os.OpenFile(fileName, os.O_CREATE|os.O_WRONLY|os.O_EXCL|os.O_SYNC, 0700)
if err != nil {
  return err
}

pemfd, err := pemaead.NewWriter(fd, password, pemaead.CipherAESGCM, pemaead.DerivateArgon2)
if err != nil {
  return err
}
defer pemfd.Close()
...
_, err = pemfd.Write(data)
if err != nil {
  return err
}
...

Reader

...
fd, err := os.Open(fileName)
if err != nil {
  return err
}

pemfd, err := pemaead.NewReader(fd, password)
if err != nil {
  return err
}
defer pemfd.Close()

data, err := ioutil.ReadAll(pemfd)
if err != nil {
  return err
}