Designed by Ron Rivest, RSA was originally part of RSA Security and is a patented cryptographic product. It is a byte-oriented stream cipher with a variable key length that is very simple, but it works. The RC4 algorithm is widely used in the SSL/TLS protocol and the WEP/WPA protocol.
RC4 mainly consists of three processes
- Initialize the S and T arrays.
- Initialize the replacement S.
- Generate a key stream.
Initializing S and T arrays¶
The code to initialize S and T is as follows
for i = 0 to 255 do S[i] = i T[i] = K[i mod keylen])
Initialization replacement S¶
j = 0 for i = 0 to 255 do j = (j + S[i] + T[i]) (mod 256) swap (S[i], S[j])
Generating a stream key¶
i = j = 0 for each message byte b i = (i + 1) (toward 256) j = (j + S[i]) (mod 256) swap(S[i], S[j]) t = (S[i] + S[j]) (mod 256) print S[t]
We generally refer to the first two parts as KSA and the last part to PRGA.
To be added.
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