How can I extend the RSA LSB Oracle attack, to n-LSBs?

uy flag

Suppose we have an RSA-Oracle that can encrypt and decrypt our input. The the decryption output is equal to: $ (C^d \mod N) \mod 2^n $.
How can I extend the LSB oracle attack, using the using knowledge about the last n-bits of the plaintext?

fgrieu avatar
ng flag
If think the question assumes an RSA decryption oracle accepting $C$, giving $(C^d\bmod N)\bmod2^n$ for $n>1$; and the Q wants to optimize the number of queries to decipher one ciphertext compared to [this question]( Critic: In RSA, encryption is with the public key, and availability of an encrypting oracle follows (and needs not be an assumption as in the Q).
fgrieu avatar
ng flag
Again: the attack with $n=1$ is discussed [there]( Also, a never related question is [there]( But until it's clarified what the present question asks, I can't be quite sure one is a dupe of the other.
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