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module rc4
// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
// Package rc4 implements RC4 encryption, as defined in Bruce Schneier's
// Applied Cryptography.
//
// RC4 is cryptographically broken and should not be used for secure
// applications.
// Based off: https://github.com/golang/go/blob/master/src/crypto/rc4
// Last commit: https://github.com/golang/go/commit/b35dacaac57b039205d9b07ea24098e2c3fcb12e
import crypto.internal.subtle
// A Cipher is an instance of RC4 using a particular key.
struct Cipher {
mut:
s []u32
i byte
j byte
}
// new_cipher creates and returns a new Cipher. The key argument should be the
// RC4 key, at least 1 byte and at most 256 bytes.
pub fn new_cipher(key []byte) ?Cipher {
if key.len < 1 || key.len > 256 {
return error('crypto.rc4: invalid key size ' + key.len.str())
}
mut c := Cipher{
s: []u32{len: (256)}
}
for i in 0 .. 256 {
c.s[i] = u32(i)
}
mut j := byte(0)
for i in 0 .. 256 {
j += byte(c.s[i]) + key[i % key.len]
tmp := c.s[i]
c.s[i] = c.s[j]
c.s[j] = tmp
}
return c
}
// reset zeros the key data and makes the Cipher unusable.good to com
//
// Deprecated: Reset can't guarantee that the key will be entirely removed from
// the process's memory.
pub fn (mut c Cipher) reset() {
for i in c.s {
c.s[i] = 0
}
c.i = 0
c.j = 0
}
// xor_key_stream sets dst to the result of XORing src with the key stream.
// Dst and src must overlap entirely or not at all.
pub fn (mut c Cipher) xor_key_stream(mut dst []byte, mut src []byte) {
if src.len == 0 {
return
}
if subtle.inexact_overlap(dst, src) {
panic('crypto.rc4: invalid buffer overlap')
}
mut i := c.i
mut j := c.j
for k, v in src {
i += byte(1)
x := c.s[i]
j += byte(x)
y := c.s[j]
c.s[i] = y
c.s[j] = x
dst[k] = v ^ byte(c.s[byte(x + y)])
}
c.i = i
c.j = j
}
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