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0

I am planning to develop a more secure version of the RC4 algorithm. Since I´m not an encryption expert... Never roll your own crypto, especially not if you are no expert in that topic. There are so many traps, starting from implementation bugs to side channel attacks. Simply use existing crypto libraries of secure algorithms like AES.

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Does the value of the key array(T) have to be in this range [0-255] if yes could you please specify why? Yes. RC4 operates on bytes. There are 256 possible values for an 8 bit (1 byte) number, that range from 0 to 255. RC4 treats the key as an array of bytes, so every entry in the key array is by definition in the range 0 to 255. Why did they use ...

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Don't know if this is still of interest. The fastest way I see is to precompute a basis $E_i=M^{2^i}*E$ for $i=1,...,n$ and then to solve the system of linear equations: $$S = c_1*E_1 +...+c_n*E_n$$ The values $c_i$ give you the binary representation of $N$. The effort is $n^3$ (for the online step) and memory requirement should be roughly $n^3$ as well. ...

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No. Indeed, as in the answer by Maarten, it depends on the security and strength of the stream cipher. However, even if the stream cipher is a secure pseudorandom generator (which is its proper modeling), encryption is not necessarily CPA-secure when XORing the pad with the plaintext. This is also explained in great detail in Katz-Lindell. In fact, it is ...

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No. There is a difference between the type of a cipher and the construction of a cipher. If a cipher is of a specific type for which there are known IND-CPA secure constructions then that doesn't mean that an entirely different construction is secure. There are known attacks on stream ciphers, including "modern" stream ciphers such as RC4. If the generated ...

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