2018-02-16T22:25:45Z
The following are code examples for showing how to use Crypto.PublicKey.RSA.generate.They are from open source Python projects. You can vote up the examples you like or vote down the ones you don't like.
Posted by Miguel Grinberg under Security, Programming, Python.
When working with web applications, it is often necessary to generate passwords, tokens or API keys, to be assigned to clients to use as authentication. While there are many sophisticated ways to generate these, in many cases it is perfectly adequate to use sufficiently long and random sequences of characters. The problem is that if you are doing this in Python, there is more than one way to generate random strings, and it isn't always clear which way is the best and most secure.
You would think that adding yet one more method to generate random strings would confuse things even more, but unlike all the other options, the new
secrets module introduced in Python 3.6 is actually designed for this specific use case, so from my part it is a welcome addition to the Python standard library. In this short article I'm going to give you an overview of this new module.
Generating Tokens
The
secrets module is part of the Python standard library in Python 3.6 and newer. You can import this module into your application or into a Python shell as follows:
At the core of this module there are three functions that generate random tokens using the best random number generator provided by your system. The first function generates binary sequences of random bytes:
Invoking the
token_bytes() function without any arguments returns a token with a default length that is determined to be sufficiently safe and secure. You can also pass the desired length as an argument, as you can see in the second example above.
The
token_hex() function works in a similar way, but returns a string with the bytes rendered in hexadecimal notation instead of a raw binary string:
Generate Secret Key Python Flask
With this function, each byte in the sequence is rendered as two hexadecimal digits, so in the second example above, where I request a token with 20 characters, the resulting string is going to be 40 characters long.
The third function in this group is
token_urlsafe() , which returns the random string encoded in base64 format:
The base64 encoding is more efficient than hexadecimal. In the example above you can see that when I requested a token of 20 characters, the resulting base64 encoded string is 27 characters long.
How to know when to use each of these functions? For most cases, the
token_urlsafe() function is probably the best option, so start from that one. If you prefer random strings encoded in hexadecimal notation (which will give you only characters in the 0-9 and a-f ranges) then use token_hex() . Finally, if you prefer a raw binary string, without any encodings, then use token_bytes() .
There are many use cases that benefit from have a simple and secure way to generate tokens. Here are a few examples:
Generating Random Numbers
While the token generation functions I described in the previous section are the most useful, the
secrets module also provides a few functions that deal with random numbers.
The
choice() function returns a randomly selected item from the list provided as an argument:
Python Flask Secret Key![]()
This function can be combined with a list comprehension to generate random strings that only use a specific set of characters. For example, if you want to generate a random string of 20 characters that only uses the letters
abcd you can do so as follows:
The
randbelow() function generates a random integer number between 0 and the number given as an argument (not including this number):
Finally, the
randbits() function returns an random integer number that has the specified number of bits:
Conclusion
I hope you found this little article useful. I find the token generation functions, and in particular
token_urlsafe() , very convenient and keep discovering new uses for it. Are you using these functions for an original purpose I have not described in this article? Let me know below in the comments!
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