1// eax.cpp - written and placed in the public domain by Wei Dai
2
3#include "pch.h"
4#include "eax.h"
5
6NAMESPACE_BEGIN(CryptoPP)
7
8void EAX_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs &params)
9{
10	AccessMAC().SetKey(userKey, keylength, params);
11	m_buffer.New(2*AccessMAC().TagSize());
12}
13
14void EAX_Base::Resync(const byte *iv, size_t len)
15{
16	MessageAuthenticationCode &mac = AccessMAC();
17	unsigned int blockSize = mac.TagSize();
18
19	memset(m_buffer, 0, blockSize);
20	mac.Update(m_buffer, blockSize);
21	mac.CalculateDigest(m_buffer+blockSize, iv, len);
22
23	m_buffer[blockSize-1] = 1;
24	mac.Update(m_buffer, blockSize);
25
26	m_ctr.SetCipherWithIV(AccessMAC().AccessCipher(), m_buffer+blockSize, blockSize);
27}
28
29size_t EAX_Base::AuthenticateBlocks(const byte *data, size_t len)
30{
31	AccessMAC().Update(data, len);
32	return 0;
33}
34
35void EAX_Base::AuthenticateLastHeaderBlock()
36{
37	assert(m_bufferedDataLength == 0);
38	MessageAuthenticationCode &mac = AccessMAC();
39	unsigned int blockSize = mac.TagSize();
40
41	mac.Final(m_buffer);
42	xorbuf(m_buffer+blockSize, m_buffer, blockSize);
43
44	memset(m_buffer, 0, blockSize);
45	m_buffer[blockSize-1] = 2;
46	mac.Update(m_buffer, blockSize);
47}
48
49void EAX_Base::AuthenticateLastFooterBlock(byte *tag, size_t macSize)
50{
51	assert(m_bufferedDataLength == 0);
52	MessageAuthenticationCode &mac = AccessMAC();
53	unsigned int blockSize = mac.TagSize();
54
55	mac.TruncatedFinal(m_buffer, macSize);
56	xorbuf(tag, m_buffer, m_buffer+blockSize, macSize);
57}
58
59NAMESPACE_END
60