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Should I use ECB or CBC encryption mode for my block cipher?

up vote 14 down vote favorite

Can someone tell me which mode out of ECB and CBC is better, and how to decide which mode to use? Are there any other modes which are better?

Edit: This question was asked long back when I was working on a Flex application to enrypt/decrypt files.

2 Answers

up vote 4 down vote accept

ECB is not secure, it leaks information. CBC is better. But if you need random access to your file Use CTR mode.

For more information about Block cipher modes of operation see the Wikipedia article.

up vote 3 down vote

Never use ECB! It is insecure.

I recommend an authenticated encryption mode, like EAX or GCM. If you can't use authenticated encryption, use CBC or CTR mode encryption, and then apply a MAC (e.g., AES-CMAC or SHA1-HMAC) to the resulting ciphertext.


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Should I use ECB or CBC encryption mode for my block cipher?

up vote 14 down vote

Can someone tell me which mode out of ECB and CBC is better, and how to decide which mode to use? Are there any other modes which are better?

Edit: This question was asked long back when I was working on a Flex application to enrypt/decrypt files.


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up vote 9 down vote

ECB is not secure, it leaks information. CBC is better. But if you need random access to your file Use CTR mode.

For more information about Block cipher modes of operation see the Wikipedia article.

edit

Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. "ECB is not secure, it leaks information" is a conclusion, but not including what's going on that makes that the right conclusion puts us in a "give a man a fish" vs. "teach a man to fish" scenario -- it's always better to teach him to fish. :) - HedgeMage Jul 25 '11 at 17:51

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