1// rc6.cpp - written and placed in the public domain by Sean Woods
2// based on Wei Dai's RC5 code.
3
4#include "pch.h"
5#include "rc6.h"
6#include "misc.h"
7
8NAMESPACE_BEGIN(CryptoPP)
9
10void RC6::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs &params)
11{
12	AssertValidKeyLength(keylen);
13
14	r = GetRoundsAndThrowIfInvalid(params, this);
15	sTable.New(2*(r+2));
16
17	static const RC6_WORD MAGIC_P = 0xb7e15163L;    // magic constant P for wordsize
18	static const RC6_WORD MAGIC_Q = 0x9e3779b9L;    // magic constant Q for wordsize
19	static const int U=sizeof(RC6_WORD);
20
21	const unsigned int c = STDMAX((keylen+U-1)/U, 1U);	// RC6 paper says c=1 if keylen==0
22	SecBlock<RC6_WORD> l(c);
23
24	GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen);
25
26	sTable[0] = MAGIC_P;
27	for (unsigned j=1; j<sTable.size();j++)
28		sTable[j] = sTable[j-1] + MAGIC_Q;
29
30	RC6_WORD a=0, b=0;
31	const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c);
32
33	for (unsigned h=0; h < n; h++)
34	{
35		a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3);
36		b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
37	}
38}
39
40typedef BlockGetAndPut<RC6::RC6_WORD, LittleEndian> Block;
41
42void RC6::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
43{
44	const RC6_WORD *sptr = sTable;
45	RC6_WORD a, b, c, d, t, u;
46
47	Block::Get(inBlock)(a)(b)(c)(d);
48	b += sptr[0];
49	d += sptr[1];
50	sptr += 2;
51
52	for(unsigned i=0; i<r; i++)
53	{
54		t = rotlFixed(b*(2*b+1), 5);
55		u = rotlFixed(d*(2*d+1), 5);
56		a = rotlMod(a^t,u) + sptr[0];
57		c = rotlMod(c^u,t) + sptr[1];
58		t = a; a = b; b = c; c = d; d = t;
59		sptr += 2;
60	}
61
62	a += sptr[0];
63	c += sptr[1];
64
65	Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
66}
67
68void RC6::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
69{
70	const RC6_WORD *sptr = sTable.end();
71	RC6_WORD a, b, c, d, t, u;
72
73	Block::Get(inBlock)(a)(b)(c)(d);
74
75	sptr -= 2;
76	c -= sptr[1];
77	a -= sptr[0];
78
79	for (unsigned i=0; i < r; i++)
80	{
81		sptr -= 2;
82		t = a; a = d; d = c; c = b; b = t;
83		u = rotlFixed(d*(2*d+1), 5);
84		t = rotlFixed(b*(2*b+1), 5);
85		c = rotrMod(c-sptr[1], t) ^ u;
86		a = rotrMod(a-sptr[0], u) ^ t;
87	}
88
89	sptr -= 2;
90	d -= sTable[1];
91	b -= sTable[0];
92
93	Block::Put(xorBlock, outBlock)(a)(b)(c)(d);
94}
95
96NAMESPACE_END
97