Generated number length?

[ioleo]

Is it possible to control the generated number length?

Eg. say I need 7-digits unique numbers, generated based on some integer eg.

  1 --> 1234567
 23 --> 7654321
100 --> 0112110

?

[mtangoo]

I'm interested also to this. Is it possible to generate fixed length numbers or at least know the length of the number in terms of range?

[ioleo]

@mtangoo I actually created my own library for this loostro/cryptomute - an implementation of Format Preserving Encryption based on Feistel Ciphers.

[jenssegers]

The maximum value is controlled by the const MAX_INT = 2147483647; value. But there is no easy way of overwriting that value at this moment.

But you could try extending the class and overwriting the MAX_INT value.

[jenssegers]

Could you also elaborate on the use case?

[mtangoo]

Suppose you generate something like Student ID. You want all student IDs to have same length in digits despite their real IDs. Another example might be a bank account @jenssegers

[mtangoo]

@loostro If I happen to have a Billion IDs will there be a collision with your library?

[ioleo]

@mtangoo no, there will be none. Read on Formart Preserving Encryption

[mtangoo]

@loostro thanks.

[EthraZa]

You may do:

$myId = str_pad($optimusId, 7, 0, STR_PAD_LEFT);

[jonagoldman]

any updates on this?

[courtney-miles]

PR #36 introduces flexibility around this.

Note that from what I could see, the maths for generating the integers requires a binary numbers. This means you could restrict the numbers to 65535 but not 99999.

For anyone who desperately needs more flexibility, a similar strategy is described at A practical use of multiplicative inverses which uses Modulus rather than a Bitwise And to shift the value. I found in testing that this method allows any int to be used as a max. However it also requires the use of co-prime rather than a prime. So the strategy is not compatible with Optimus.