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Description:

privy 6.0.0

Privy is a small and fast utility for password-protecting secret data such as
API keys, cryptocurrency wallets, or seeds for digital signatures.

Table of Contents

Usage
Installation
Encryption scheme
Encrypted format
API

hide
peek

Security levels
License
Changelog

6.0.0
5.0.0
4.0.0
3.0.0
2.0.1
1.0.0

Usage
Say for example you are using GnuPG. You are about to sign a message but it first
requires your password. Does your password become the input to instantiate your
private key? No, it is first hashed by a secure key derivation function. That
hash then becomes the input to a symmetric cipher such as AES which then decrypts
your stored private key. That is what Privy does.
Fear not! With Privy, this become trivially easy:
>>> import privy
>>>
>>> # After creating secret, immediately encrypt it using Privy.
>>> data = b'secret'
>>>
>>> hidden = privy.hide(data, ask_for_password())
>>> hidden
'1$2$fL7xRh8WKe...'
Now you can safely store or transmit the hidden secret. Whenever your user needs
to use their secret again, ask for their password to take a peek.
>>> privy.peek(hidden, password)
b'secret'

Installation
Privy is available on Linux/macOS and Windows and supports Python 2.7, 3.3+, PyPy, and PyPy3.3-5.5+.
$ pip install privy

Encryption scheme
Secrets are encrypted using the Fernet protocol. Specifically, it uses AES for
encryption and has built-in authentication using HMAC. The private key used for
encryption is derived from the password using a key derivation function. The
key derivation function used is Argon2, the winner of the Password Hashing
Competition. Both Argon2i and Argon2d variants are supported.

Encrypted format
ascii(Argon2 algorithm || security level || base64(salt) || base64(Fernet token))

API
There are 2 functions: hide and peek.

hide
hide(secret, password, security=2, salt=None, server=True)
Encrypts secret using password. Returns the hidden secret as unicode.

Parameters

secret (bytes) - The secret to encrypt.
password (bytes or unicode) - The password used to access the secret.
security (int) - A number 0-20 inclusive. Higher values are more secure at
the cost of slower computation and greater use of memory. See security levels.
salt (bytes) - The salt used for the password hash. Defaults to os.urandom(32).
server (bool) - If True, it is assumed side-channel attack protection is
needed and therefore the Argon2i algorithm will be used. Otherwise, the password will
be hashed using the Argon2d algorithm.

peek
peek(hidden, password, expires=None)
Decrypts hidden using password. Returns the secret as bytes.

Parameters

hidden (bytes or unicode) - The hidden secret to decrypt.
password (bytes or unicode) - The password used to access the secret.
expires (int) - The maximum number of seconds since encryption that
is allowed. The default is no expiration.

A ValueError will be raised if the password is wrong, the password was attempted on a
different hidden secret, or the number of seconds since encryption is > expires argument.

Security levels
All expected times were taken from tests on an Intel Core i7-2670QM @ 2.2 GHz when decrypting
a 256 KiB secret.
This is the command, where SL is the desired security level:
$ python -m timeit -s "import privy, os; pw = 'password'; s = os.urandom(1024 * 256); h = privy.hide(s, pw, SL)" "privy.peek(h, pw)"

Levels
Argon2 settings
Expected time
Notes

0
m=8 KiB, t=1
7 msec
Lowest possible

1
m=4 MiB, t=10
54 msec

2
m=8 MiB, t=10
99 msec
Default

3
m=32 MiB, t=10
367 msec

4
m=48 MiB, t=10
540 msec

5
m=96 MiB, t=10
1.1 sec
Good choice

6
m=256 MiB, t=10
3 sec

7
m=512 MiB, t=10
6 sec

8
m=768 MiB, t=10
9 sec

9
m=1 GiB, t=10
12.2 sec

10
m=2 GiB, t=20
48 sec
For use on
users’ machines

11
m=3 GiB, t=30
107

12
m=4 GiB, t=40
?

13
m=5 GiB, t=50
?

14
m=6 GiB, t=60
?

15
m=7 GiB, t=70
?

16
m=8 GiB, t=80
?

17
m=9 GiB, t=90
?

18
m=10 GiB, t=100
?

19
m=11 GiB, t=110
?

20
m=12 GiB, t=120
?

License
Privy is distributed under the terms of either

MIT License
Apache License, Version 2.0

at your option.

Changelog
Important changes are emphasized.

6.0.0

Breaking: Support for Python 3.3 has been dropped.

5.0.0

Breaking: Privy is now dual-licensed under the terms of MIT and Apache v2.0.
Only documented methods hide and peek are now exposed in the root namespace.
Travis now runs tests with the latest versions of PyPy and PyPy3.
Improvements to documentation.

4.0.0

Breaking: For saner conformity, security level 7 now utilizes 512 MiB of RAM instead of 448.
Major improvements to documentation.

3.0.0

Added security levels 11-20. These are quite resource intensive and are therefore
only acceptable for individual use.

2.0.1

Breaking: Due to requests, the encrypted format now uses url-safe base64 instead of hex.

1.0.0

Initial release