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CCM puts together two different modes of operation (at least in the name). Does it mean data is encrypted using counter mode and then encrypted using CBC; kind of a double encryption?

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CCM puts together two different modes of operation (at least in the name). Does it mean data is encrypted using counter mode and then encrypted using CBC; kind of a double encryption?

Yes, kinda.
With the CCM mode of operation, you authenticate your data first using CBC-MAC which is, well, basically CBC on the data to be authenticated.

Now on the combination of ciphertext and tag you apply the CTR mode to conceal the contents. While you do "double-encryption" here, you only send the full result of the CTR mode and only the very last block from the CBC mode (encrypted using CTR). The latter one is the tag with which the recipient can verify the integrity of the message.

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  • $\begingroup$ Is a meet in the middle attack a threat to the double encryption in this case? $\endgroup$ – Minaj Oct 10 '16 at 21:37
  • $\begingroup$ @Minaj, well, sure. But CCM never claimed to reach better security than each component provides so there's no point in doing one (to break security guarantees) $\endgroup$ – SEJPM Oct 10 '16 at 21:39
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    $\begingroup$ This is not an implementation of double-encryption. This is not $E(k_1, E(k_2, m))$. It is $E(k_1, m) || f(E(k_2, m))$ (where $f$ is just taking the last block). There is no "middle" to meet in here. $\endgroup$ – Stephen Touset Oct 10 '16 at 22:49

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