Introduction

idgen lets you generate unique identifiers that:

• match a desired format;

• look random (if you activate crypto);

• can be converted back to ints, given the password; and

• use ALL possible values in the forma

Let’s say you want to generate IDs like:

vis90000
suu54581
qcr00006
pcg75148
yuy22283
low69877

Feed the numbers 0-5 thru Encoder('aaaddddd', password='jupiterx').

You can reverse the process, turning these ids back into 0-5.

Questions

Q: Why not use incrementing integers as identifiers?

A: You may want to conceal from outsiders how rapidly objects are being created. You may want specific formats that use less characters than base10 but are human-friendly.

Q: Why not randomly generate identifiers?

A: If you want to avoid issuing the same id twice, you need to look up each new id in a database or map. As the number of issued ids grows, the number of lookups per new id grows. If you only plan to use a tiny portion of the available keyspace, this is acceptable, but inelegant compared to just encrypting an int.

Q: Why not just encrypt an integer with AES or something?

A: Because the output of the block cipher is a fixed size, which is not likely to match your desired format.

A format of digits and uppercase letters, for instance, has 10**A * 26**B values.

The 128-bit outputs of AES would take 39 decimal digits to encode.

If you truncate the output of the block cipher, the ids are no longer unique or reversible.

Installation

Checkout the source and run python setup.py install.

Using Idgen

from idgen import Encoder
enc = Encoder('adad', password='Jupiterx')
id = enc.encode(13) # f6d9
i = enc.decode(id) # 13

This creates an encoder which encodes/decodes strings of the form letter-digit-letter-digit. There are 26*10*26*10 such strings, so the encoder can handle integers from 0 to n-1.

enc = Encoder('wpwpw', types={'w': 'VWXYZ', 'p': '!@#$%^&*()'}, password='Jupitery')
for i in range(5):
  print enc.encode(i)

X$X&X
Y%W(W
V!W$V
Z)V@Y
V)X)X

enc = Encoder('aaa')
for i in range(200, 205):
  print enc.encode(i)

ahs
aht
ahu
ahv
ahw

enc = Encoder('ad/ddd-a.d', password='Jupiterz')
for i in range(5):
  print enc.encode(i)

j7/739-l.5
x2/319-z.2
w9/274-i.8
z5/166-m.9
v3/500-p.3