1// rc5.cpp - written and placed in the public domain by Wei Dai
2
3#include "pch.h"
4#include "rc5.h"
5#include "misc.h"
6
7NAMESPACE_BEGIN(CryptoPP)
8
9void RC5::Base::UncheckedSetKey(const byte *k, unsigned int keylen, const NameValuePairs &params)
10{
11	AssertValidKeyLength(keylen);
12
13	r = GetRoundsAndThrowIfInvalid(params, this);
14	sTable.New(2*(r+1));
15
16	static const RC5_WORD MAGIC_P = 0xb7e15163L;    // magic constant P for wordsize
17	static const RC5_WORD MAGIC_Q = 0x9e3779b9L;    // magic constant Q for wordsize
18	static const int U=sizeof(RC5_WORD);
19
20	const unsigned int c = STDMAX((keylen+U-1)/U, 1U);	// RC6 paper says c=1 if keylen==0
21	SecBlock<RC5_WORD> l(c);
22
23	GetUserKey(LITTLE_ENDIAN_ORDER, l.begin(), c, k, keylen);
24
25	sTable[0] = MAGIC_P;
26	for (unsigned j=1; j<sTable.size();j++)
27		sTable[j] = sTable[j-1] + MAGIC_Q;
28
29	RC5_WORD a=0, b=0;
30	const unsigned n = 3*STDMAX((unsigned int)sTable.size(), c);
31
32	for (unsigned h=0; h < n; h++)
33	{
34		a = sTable[h % sTable.size()] = rotlFixed((sTable[h % sTable.size()] + a + b), 3);
35		b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
36	}
37}
38
39typedef BlockGetAndPut<RC5::RC5_WORD, LittleEndian> Block;
40
41void RC5::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
42{
43	const RC5_WORD *sptr = sTable;
44	RC5_WORD a, b;
45
46	Block::Get(inBlock)(a)(b);
47	a += sptr[0];
48	b += sptr[1];
49	sptr += 2;
50
51	for(unsigned i=0; i<r; i++)
52	{
53		a = rotlMod(a^b,b) + sptr[2*i+0];
54		b = rotlMod(a^b,a) + sptr[2*i+1];
55	}
56
57	Block::Put(xorBlock, outBlock)(a)(b);
58}
59
60void RC5::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
61{
62	const RC5_WORD *sptr = sTable.end();
63	RC5_WORD a, b;
64
65	Block::Get(inBlock)(a)(b);
66
67	for (unsigned i=0; i<r; i++)
68	{
69		sptr-=2;
70		b = rotrMod(b-sptr[1], a) ^ a;
71		a = rotrMod(a-sptr[0], b) ^ b;
72	}
73	b -= sTable[1];
74	a -= sTable[0];
75
76	Block::Put(xorBlock, outBlock)(a)(b);
77}
78
79NAMESPACE_END
80