Score:1

Securing counter value for OTP

za flag

I'm working on a project that needs an OTP based on counter value and needs some advice.

Suppose we encrypt the counter value C in this way and let's say our sending packet is P = AES(key,C). If counter value C is leaked, will this cause a security problem? I tried to find some papers regarding this but failed.

Thank you!

ph flag
I think you are asking about https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_(CTR)? In which case "CTR mode" is the phrase to search for.
SAI Peregrinus avatar
si flag
A One-Time Pad doesn't use a counter (by definition). One-Time Password systems also don't typically use a counter. What definition of "OTP" are you using?
Maarten Bodewes avatar
in flag
I’m voting to close this question for now because the question both specifies one-time-pad and Hash based One Time Password. Please indicate which scheme is meant by hitting [edit].
Score:1
cn flag

If P = AES(key,C) and then we do AES(key,C) again, how can that possibly be a one time pad? The generated cipher text for each block encrypt will repeat which means that the keystream is entirely deterministic.

Sometimes the term 'one time pad' is used interchangeably with stream ciphers. However, one time pad keystreams are not deterministic. So, if you were hoping for information-theoretically secure encryption then using a counter based key stream has problems.

You have tagged the question with one time pad, but please read the similarly tagged Q&As.

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