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desirepath41 / visualCaptcha

visualCaptcha's Main Repo. This is a collection of all the different versions/repos of visualCaptcha.
https://emotionloop.github.io/visualCaptcha-demo/
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Security improvement for brute-force collection #2

Closed BrunoBernardino closed 9 years ago

BrunoBernardino commented 10 years ago

We should make a change in all back-end packages:

Add a random length of garbage information (just 1-50 bytes, for example) to any image when showing it, so the image sizes/hashes would never be the same if someone tries to download and create a database of image -> checksum.

oujesky commented 10 years ago

I fear that simple change in signature is not enough for a brute force counter-measure. The content of the image can be quite easily compared visually using a tool like http://phash.org/ against a predefined set of images. Then the difference in file checksum won't have any effect.

BrunoBernardino commented 10 years ago

@oujesky thank you so much for your feedback. You can look at #8 for some of the counter points I made there.

Do you have a suggestion that won't cripple UX, and solve the problem you're talking about?

jasny commented 9 years ago

Note that even with just guessing, one in five attempts will succeed (or worse #17).

Having a single image where the images are randomly placed already makes it more difficult, storing the correct coordinates in the session. Adding a non-white background might make it secure enough. At least to keep out casual hackers.

Click on the printer alt

BrunoBernardino commented 9 years ago

I like this concept. Delivering one single generated image instead. It will increase the server processing and requirements, but should not be a big deal. As for accessibility concerns (for color-blind), the accessibility option should be a good alternative.

Maybe the front-end can set the image size and number of images to deliver, and the server will have a reasonable limit for both options (as per #17).

Sounds good?

BrunoBernardino commented 9 years ago

After some deliberation, I've went with the simpler option to increase the file size randomly, in order to not cripple the UX.

The main goal of visualCaptcha is to be extremely user-friendly and accessible, even if that means not being the most secure option out there. There's a very good one for that already (reCaptcha).

CrazyPython commented 8 years ago

@BrunoBernardino You should add some image corruption to make it harder for hackers to crack, for example adding random colored dots to the image and changing the color of the image. That would make it significantly more secure.

BrunoBernardino commented 8 years ago

@CrazyPython Thank you for your suggestion. That's been discussed before and discarded in the comment above.