PHP: Minify crypted value

Question

Is it possible, to transform a crypted string (similar to md5), without loosing the ability of decoding it back again?

0TJyj0wX4ZCrsYlANG8QgwBHnGzGU7kr1BEkolr6tY0OdowpA==

Better: 73a4842f36b4n237m64as23

By nature, a hash is one direction. You're looking for a transformation (or potentially encryption.) — Corbin, Mar 21 '12 at 20:54
If you want to decode it we are probably talking about encryption. How secure do you want it to be? — Tchoupi, Mar 21 '12 at 21:00
You could just encode/decode and compare the first (or last) bytes returned by `crypt`, but you would get less secure with each byte you remove...otherwise you can only go with Justin's answer I think. — Maarten Bodewes, Mar 21 '12 at 22:08
I have a suspicion that the problem you are trying to solve might be approached in a different way than trying to compress encrypted data. I'd suggest posting a new question with some more detail about what you're trying to achieve. If you do so, link to it here in the comments. — Justin ᚅᚔᚈᚄᚒᚔ, Mar 22 '12 at 15:13

score 2 · Accepted Answer · edited May 23 '17 at 12:27

2

A hash is, by definition, one-way. You would not be able to hash your crypted string and then "un-hash" it to obtain the crypted string again.

You can, however, attempt to "minify" the crypted string by:

Using a lossless compression algorithm -- though you're unlikely to gain much with this approach since encrypted data doesn't compress well, and for certain input sets compression can actually increase the storage requirements.
Compress the data before encrypting it. Depending on the size of input, it's possible to reduce the size by a few percent over encryption alone (depending on the algorithms), but typically not by more than 5-10% (again, this answer points this out)
Re-encoding the data with a higher "base" (i.e. your string is Base64, you could switch to Base85) -- but this only results in a 7% savings

edited May 23 '17 at 12:27

Community

answered Mar 21 '12 at 20:58

1

Lossless compression won't work too well on hashed or encrypted data either, the data will look like random data to the compression algorithm. It's worse than trying to zip a JPEG or MP3 file. – Maarten Bodewes Mar 21 '12 at 22:03
@owlstead: +1 True, I should have noted that in the answer... edit time! – Justin ᚅᚔᚈᚄᚒᚔ Mar 22 '12 at 14:52
Because msec doesn't tell where he need it -> He could encode it binary – mabe.berlin Apr 05 '12 at 15:06
@mabe: Technically speaking, the data *is* in binary -- the string is just a representation of that binary data. The encoding is what specifies how that binary data is represented: hexadecimal (base16), base64, base85. The phrase "encode in binary" doesn't make a lot of sense, unless I'm misunderstanding your meaning. – Justin ᚅᚔᚈᚄᚒᚔ Apr 05 '12 at 15:29

score 0 · Answer 2 · answered Mar 21 '12 at 20:57

0

you can use RSA to encrypt you data see this, it talks about to crypt in php

answered Mar 21 '12 at 20:57

Jayyrus

score 0 · Answer 3 · answered Mar 21 '12 at 21:11

0

Best way to encrypt in PHP is by using the Mcrypt extension. http://www.php.net/manual/en/book.mcrypt.php

I do recommend also to base64 encode the result of encryption.

Minification does not make sense for small data (ex. passwords).

answered Mar 21 '12 at 21:11

Dragos

I don't think the generic encryption/decryption samples are useful. I would +1 if you would have just posted the last sentence. – Maarten Bodewes Mar 21 '12 at 22:05

3 Answers3