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* updated README.md: - corrected information about encryption - made additions based on proposed changes to overview.md - made other changes for clarity and grammar * ongoing changes to overview.md * added note that `pycrypto` is required made other small changes for grammar and clarity * added new python decryption script to encryption.md * updated encryption.md to clarify dependencies other relatively small changes for clarity straightened quotes Co-authored-by: Guy B. deBros <guydebros@users.noreply.github.com>
136 lines
3.9 KiB
Markdown
136 lines
3.9 KiB
Markdown
# Encryption
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## A Note on Security
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While `jrnl` follows best practices, total security is never possible in the
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real world. There are a number of ways that people can at least partially
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compromise your `jrnl` data. See the [Privacy and Security](./security.md) page
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for more information.
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## Dependencies
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As of version 2.0, `jrnl`'s encryption functions require
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[`cryptography`](https://pypi.org/project/cryptography/), which is available in
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the Python Package Index (PyPI) and can be installed using `pip`:
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``` sh
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pip3 install cryptography
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```
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Previous versions of `jrnl` require
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[`pycrypto`](https://pypi.org/project/pycrypto/):
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```sh
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pip3 install pycrypto
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```
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## Encrypting and Decrypting
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Existing plain text journal files can be encrypted using the `--encrypt`
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command:
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``` sh
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jrnl --encrypt [FILENAME]
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```
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You can then enter a new password, and the unencrypted file will replaced with
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the new encrypted file.
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This command also works to change the password for a journal file that is
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already encrypted. `jrnl` will prompt you for the current password and then new
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password.
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Conversely,
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``` sh
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jrnl --decrypt [FILENAME]
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```
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replaces the encrypted journal file with a plain text file. You can also specify
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a filename, e.g., `jrnl --decrypt plain_text_copy.txt`, to leave the original
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encrypted file untouched and create a new plain text file next to it.
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## Storing Passwords in Your Keychain
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There is no method to recover or reset your `jrnl` password. If you lose it,
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your data will be inaccessible forever.
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For this reason, when encrypting a journal, `jrnl` asks whether you would like
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to store the password in your system's keychain. An added benefit is that you
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will not need to enter the password when interacting with the journal file.
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If you don't initially store the password in your keychain but decide to do so
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later---or if you want to store it in one computer's keychain but not in another
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computer's---you can run `jrnl --encrypt` on an encrypted journal and use the
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same password again. This will trigger the keychain storage prompt.
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## Manual Decryption
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Should you ever want to decrypt your journal manually, you can do so with any
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program that supports the AES algorithm in CBC. The key used for encryption is
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the SHA-256 hash of your password. The IV (initialization vector) is stored in
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the first 16 bytes of the encrypted file. The plain text is encoded in UTF-8 and
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padded according to PKCS\#7 before being encrypted.
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Here is a Python script that you can use to decrypt your journal:
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``` python
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#!/usr/bin/env python3
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import base64
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import getpass
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from pathlib import Path
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from cryptography.fernet import Fernet
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
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filepath = input("journal file path: ")
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password = getpass.getpass("Password: ")
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with open(Path(filepath),"rb") as f:
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ciphertext = f.read()
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password = password.encode("utf-8")
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kdf = PBKDF2HMAC(
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algorithm=hashes.SHA256(),
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length=32,
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salt=b"\xf2\xd5q\x0e\xc1\x8d.\xde\xdc\x8e6t\x89\x04\xce\xf8",
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iterations=100_000,
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backend=default_backend(),
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)
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key = base64.urlsafe_b64encode(kdf.derive(password))
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print(Fernet(key).decrypt(ciphertext).decode('utf-8'))
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```
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If you're still using `jrnl` version 1.X, the following script serves the same
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purpose:
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``` python
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#!/usr/bin/env python3
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import argparse
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from Crypto.Cipher import AES
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import getpass
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import hashlib
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import sys
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parser = argparse.ArgumentParser()
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parser.add_argument("filepath", help="journal file to decrypt")
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args = parser.parse_args()
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pwd = getpass.getpass()
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key = hashlib.sha256(pwd.encode('utf-8')).digest()
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with open(args.filepath, 'rb') as f:
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ciphertext = f.read()
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crypto = AES.new(key, AES.MODE_CBC, ciphertext[:16])
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plain = crypto.decrypt(ciphertext[16:])
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plain = plain.strip(plain[-1:])
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plain = plain.decode("utf-8")
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print(plain)
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```
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