Crypto++  8.2
Free C++ class library of cryptographic schemes
dmac.h
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1 // dmac.h - originally written and placed in the public domain by Wei Dai
2 
3 /// \file dmac.h
4 /// \brief Classes for DMAC message authentication code
5 
6 #ifndef CRYPTOPP_DMAC_H
7 #define CRYPTOPP_DMAC_H
8 
9 #include "cbcmac.h"
10 
11 NAMESPACE_BEGIN(CryptoPP)
12 
13 /// \brief DMAC message authentication code base class
14 /// \tparam T class derived from BlockCipherDocumentation
15 /// \since Crypto++ 3.1
16 template <class T>
17 class CRYPTOPP_NO_VTABLE DMAC_Base : public SameKeyLengthAs<T>, public MessageAuthenticationCode
18 {
19 public:
20  CRYPTOPP_CONSTANT(DIGESTSIZE=T::BLOCKSIZE)
21  static std::string StaticAlgorithmName() {return std::string("DMAC(") + T::StaticAlgorithmName() + ")";}
22 
23  virtual~DMAC_Base() {}
24  DMAC_Base() : m_subkeylength(0), m_counter(0) {}
25 
26  void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
27  void Update(const byte *input, size_t length);
28  void TruncatedFinal(byte *mac, size_t size);
29  unsigned int DigestSize() const {return DIGESTSIZE;}
30 
31  std::string AlgorithmProvider() const;
32 
33 private:
34  byte *GenerateSubKeys(const byte *key, size_t keylength);
35 
36  size_t m_subkeylength;
37  SecByteBlock m_subkeys;
38  CBC_MAC<T> m_mac1;
39  typename T::Encryption m_f2;
40  unsigned int m_counter;
41 };
42 
43 template <class T>
45 {
46  return m_f2.AlgorithmProvider();
47 }
48 
49 /// \brief DMAC message authentication code
50 /// \tparam T class derived from BlockCipherDocumentation
51 /// \sa <A HREF="https://eprint.iacr.org/1997/010">CBC MAC for Real-Time Data Sources (08.15.1997)</A>
52 /// by Erez Petrank and Charles Rackoff
53 /// \since Crypto++ 3.1
54 template <class T>
55 class DMAC : public MessageAuthenticationCodeFinal<DMAC_Base<T> >
56 {
57 public:
58  /// \brief Construct a DMAC
59  DMAC() {}
60 
61  /// \brief Construct a DMAC
62  /// \param key a byte array used to key the cipher
63  /// \param length the size of the byte array, in bytes
64  DMAC(const byte *key, size_t length=DMAC_Base<T>::DEFAULT_KEYLENGTH)
65  {this->SetKey(key, length);}
66 };
67 
68 template <class T>
69 void DMAC_Base<T>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
70 {
71  m_subkeylength = T::StaticGetValidKeyLength(T::BLOCKSIZE);
72  m_subkeys.resize(2*UnsignedMin((unsigned int)T::BLOCKSIZE, m_subkeylength));
73  m_mac1.SetKey(GenerateSubKeys(key, length), m_subkeylength, params);
74  m_f2.SetKey(m_subkeys+m_subkeys.size()/2, m_subkeylength, params);
75  m_counter = 0;
76  m_subkeys.resize(0);
77 }
78 
79 template <class T>
80 void DMAC_Base<T>::Update(const byte *input, size_t length)
81 {
82  m_mac1.Update(input, length);
83  m_counter = (unsigned int)((m_counter + length) % T::BLOCKSIZE);
84 }
85 
86 template <class T>
87 void DMAC_Base<T>::TruncatedFinal(byte *mac, size_t size)
88 {
89  ThrowIfInvalidTruncatedSize(size);
90 
91  byte pad[T::BLOCKSIZE];
92  byte padByte = byte(T::BLOCKSIZE-m_counter);
93  memset(pad, padByte, padByte);
94  m_mac1.Update(pad, padByte);
95  m_mac1.TruncatedFinal(mac, size);
96  m_f2.ProcessBlock(mac);
97 
98  m_counter = 0; // reset for next message
99 }
100 
101 template <class T>
102 byte *DMAC_Base<T>::GenerateSubKeys(const byte *key, size_t keylength)
103 {
104  typename T::Encryption cipher(key, keylength);
105  memset(m_subkeys, 0, m_subkeys.size());
106  cipher.ProcessBlock(m_subkeys);
107  m_subkeys[m_subkeys.size()/2 + T::BLOCKSIZE - 1] = 1;
108  cipher.ProcessBlock(m_subkeys+m_subkeys.size()/2);
109  return m_subkeys;
110 }
111 
112 NAMESPACE_END
113 
114 #endif
void TruncatedFinal(byte *mac, size_t size)
Computes the hash of the current message.
Definition: dmac.h:87
Interface for message authentication codes.
Definition: cryptlib.h:1295
virtual void SetKey(const byte *key, size_t length, const NameValuePairs &params=g_nullNameValuePairs)
Sets or reset the key of this object.
Definition: cryptlib.cpp:59
DMAC message authentication code.
Definition: dmac.h:55
virtual void TruncatedFinal(byte *digest, size_t digestSize)=0
Computes the hash of the current message.
DMAC()
Construct a DMAC.
Definition: dmac.h:59
DMAC message authentication code base class.
Definition: dmac.h:17
Provides class member functions to key a message authentication code.
Definition: seckey.h:370
SecBlock<byte> typedef.
Definition: secblock.h:1058
Classes for CBC MAC.
unsigned int DigestSize() const
Provides the digest size of the hash.
Definition: dmac.h:29
virtual std::string AlgorithmProvider() const
Retrieve the provider of this algorithm.
Definition: cryptlib.h:637
DMAC(const byte *key, size_t length=DMAC_Base< T >::DEFAULT_KEYLENGTH)
Construct a DMAC.
Definition: dmac.h:64
void Update(const byte *input, size_t length)
Updates a hash with additional input.
Definition: dmac.h:80
const T1 UnsignedMin(const T1 &a, const T2 &b)
Safe comparison of values that could be neagtive and incorrectly promoted.
Definition: misc.h:647
Provides key lengths based on another class's key length.
Definition: seckey.h:217
void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
Sets the key for this object without performing parameter validation.
Definition: dmac.h:69
Crypto++ library namespace.
std::string AlgorithmProvider() const
Retrieve the provider of this algorithm.
Definition: dmac.h:44
CBC-MAC.
Definition: cbcmac.h:43
virtual void Update(const byte *input, size_t length)=0
Updates a hash with additional input.
Interface for retrieving values given their names.
Definition: cryptlib.h:321