File: drbg.h

package info (click to toggle)
libcrypto++ 8.2.0-2
  • links: PTS
  • area: main
  • in suites: experimental
  • size: 22,780 kB
  • sloc: cpp: 105,015; sh: 7,353; asm: 5,120; makefile: 316
file content (702 lines) | stat: -rw-r--r-- 35,065 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
// drbg.h - written and placed in public domain by Jeffrey Walton.

/// \file drbg.h
/// \brief Classes for NIST DRBGs from SP 800-90A
/// \sa <A HREF="http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf">Recommendation
///   for Random Number Generation Using Deterministic Random Bit Generators, Rev 1 (June 2015)</A>
/// \since Crypto++ 6.0

#ifndef CRYPTOPP_NIST_DRBG_H
#define CRYPTOPP_NIST_DRBG_H

#include "cryptlib.h"
#include "secblock.h"
#include "hmac.h"
#include "sha.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief Interface for NIST DRBGs from SP 800-90A
/// \details NIST_DRBG is the base class interface for NIST DRBGs from SP 800-90A Rev 1 (June 2015)
/// \sa <A HREF="http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf">Recommendation
///   for Random Number Generation Using Deterministic Random Bit Generators, Rev 1 (June 2015)</A>
/// \since Crypto++ 6.0
class NIST_DRBG : public RandomNumberGenerator
{
public:
    /// \brief Exception thrown when a NIST DRBG encounters an error
    class Err : public Exception
    {
    public:
        explicit Err(const std::string &c, const std::string &m)
        : Exception(OTHER_ERROR, c + ": " + m) {}
    };

public:
    virtual ~NIST_DRBG() {}

    /// \brief Determines if a generator can accept additional entropy
    /// \return true
    /// \details All NIST_DRBG return true
    virtual bool CanIncorporateEntropy() const {return true;}

    /// \brief Update RNG state with additional unpredictable values
    /// \param input the entropy to add to the generator
    /// \param length the size of the input buffer
    /// \throws NIST_DRBG::Err if the generator is reseeded with insufficient entropy
    /// \details NIST instantiation and reseed requirements demand the generator is constructed
    ///   with at least <tt>MINIMUM_ENTROPY</tt> entropy. The byte array for <tt>input</tt> must
    ///   meet <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or
    ///   SP 800-90C</A> requirements.
    virtual void IncorporateEntropy(const byte *input, size_t length)=0;

    /// \brief Update RNG state with additional unpredictable values
    /// \param entropy the entropy to add to the generator
    /// \param entropyLength the size of the input buffer
    /// \param additional additional input to add to the generator
    /// \param additionaLength the size of the additional input buffer
    /// \throws NIST_DRBG::Err if the generator is reseeded with insufficient entropy
    /// \details IncorporateEntropy() is an overload provided to match NIST requirements. NIST
    ///   instantiation and reseed requirements demand the generator is constructed with at least
    ///   <tt>MINIMUM_ENTROPY</tt> entropy. The byte array for <tt>entropy</tt> must meet
    ///   <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or
    ///!  SP 800-90C</A> requirements.
    virtual void IncorporateEntropy(const byte *entropy, size_t entropyLength, const byte* additional, size_t additionaLength)=0;

    /// \brief Generate random array of bytes
    /// \param output the byte buffer
    /// \param size the length of the buffer, in bytes
    /// \throws NIST_DRBG::Err if a reseed is required
    /// \throws NIST_DRBG::Err if the size exceeds <tt>MAXIMUM_BYTES_PER_REQUEST</tt>
    virtual void GenerateBlock(byte *output, size_t size)=0;

    /// \brief Generate random array of bytes
    /// \param additional additional input to add to the generator
    /// \param additionaLength the size of the additional input buffer
    /// \param output the byte buffer
    /// \param size the length of the buffer, in bytes
    /// \throws NIST_DRBG::Err if a reseed is required
    /// \throws NIST_DRBG::Err if the size exceeds <tt>MAXIMUM_BYTES_PER_REQUEST</tt>
    /// \details GenerateBlock() is an overload provided to match NIST requirements. The byte
    ///   array for <tt>additional</tt> input is optional. If present the additional randomness
    ///   is mixed before generating the output bytes.
    virtual void GenerateBlock(const byte* additional, size_t additionaLength, byte *output, size_t size)=0;

    /// \brief Provides the security strength
    /// \returns The security strength of the generator, in bytes
    /// \details The equivalent class constant is <tt>SECURITY_STRENGTH</tt>
    virtual unsigned int SecurityStrength() const=0;

    /// \brief Provides the seed length
    /// \returns The seed size of the generator, in bytes
    /// \details The equivalent class constant is <tt>SEED_LENGTH</tt>. The size is
    ///   used to maintain internal state of <tt>V</tt> and <tt>C</tt>.
    virtual unsigned int SeedLength() const=0;

    /// \brief Provides the minimum entropy size
    /// \returns The minimum entropy size required by the generator, in bytes
    /// \details The equivalent class constant is <tt>MINIMUM_ENTROPY</tt>. All NIST DRBGs must
    ///   be instaniated with at least <tt>MINIMUM_ENTROPY</tt> bytes of entropy. The bytes must
    ///   meet <A HREF="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or
    ///   SP 800-90C</A> requirements.
    virtual unsigned int MinEntropyLength() const=0;

    /// \brief Provides the maximum entropy size
    /// \returns The maximum entropy size that can be consumed by the generator, in bytes
    /// \details The equivalent class constant is <tt>MAXIMUM_ENTROPY</tt>. The bytes must
    ///   meet <A HREF="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or
    ///   SP 800-90C</A> requirements. <tt>MAXIMUM_ENTROPY</tt> has been reduced from
    ///   2<sup>35</sup> to <tt>INT_MAX</tt> to fit the underlying C++ datatype.
    virtual unsigned int MaxEntropyLength() const=0;

    /// \brief Provides the minimum nonce size
    /// \returns The minimum nonce size recommended for the generator, in bytes
    /// \details The equivalent class constant is <tt>MINIMUM_NONCE</tt>. If a nonce is not
    ///   required then <tt>MINIMUM_NONCE</tt> is 0. <tt>Hash_DRBG</tt> does not require a
    ///   nonce, while <tt>HMAC_DRBG</tt> and <tt>CTR_DRBG</tt> require a nonce.
    virtual unsigned int MinNonceLength() const=0;

    /// \brief Provides the maximum nonce size
    /// \returns The maximum nonce that can be consumed by the generator, in bytes
    /// \details The equivalent class constant is <tt>MAXIMUM_NONCE</tt>. <tt>MAXIMUM_NONCE</tt>
    ///   has been reduced from 2<sup>35</sup> to <tt>INT_MAX</tt> to fit the underlying C++ datatype.
    ///   If a nonce is not required then <tt>MINIMUM_NONCE</tt> is 0. <tt>Hash_DRBG</tt> does not
    ///   require a nonce, while <tt>HMAC_DRBG</tt> and <tt>CTR_DRBG</tt> require a nonce.
    virtual unsigned int MaxNonceLength() const=0;

    /// \brief Provides the maximum size of a request to GenerateBlock
    /// \returns The the maximum size of a request to GenerateBlock(), in bytes
    /// \details The equivalent class constant is <tt>MAXIMUM_BYTES_PER_REQUEST</tt>
    virtual unsigned int MaxBytesPerRequest() const=0;

    /// \brief Provides the maximum number of requests before a reseed
    /// \returns The the maximum number of requests before a reseed, in bytes
    /// \details The equivalent class constant is <tt>MAXIMUM_REQUESTS_BEFORE_RESEED</tt>.
    ///   <tt>MAXIMUM_REQUESTS_BEFORE_RESEED</tt> has been reduced from 2<sup>48</sup> to <tt>INT_MAX</tt>
    ///   to fit the underlying C++ datatype.
    virtual unsigned int MaxRequestBeforeReseed() const=0;

protected:
    virtual void DRBG_Instantiate(const byte* entropy, size_t entropyLength,
        const byte* nonce, size_t nonceLength, const byte* personalization, size_t personalizationLength)=0;

    virtual void DRBG_Reseed(const byte* entropy, size_t entropyLength, const byte* additional, size_t additionaLength)=0;
};

// *************************************************************

/// \tparam HASH NIST approved hash derived from HashTransformation
/// \tparam STRENGTH security strength, in bytes
/// \tparam SEEDLENGTH seed length, in bytes
/// \brief Hash_DRBG from SP 800-90A Rev 1 (June 2015)
/// \details The NIST Hash DRBG is instantiated with a number of parameters. Two of the parameters,
///   Security Strength and Seed Length, depend on the hash and are specified as template parameters.
///   The remaining parameters are included in the class. The parameters and their values are listed
///   in NIST SP 800-90A Rev. 1, Table 2: Definitions for Hash-Based DRBG Mechanisms (p.38).
/// \details Some parameters have been reduce to fit C++ datatypes. For example, NIST allows upto
///   2<sup>48</sup> requests before a reseed. However, Hash_DRBG limits it to <tt>INT_MAX</tt> due
///   to the limited data range of an int.
/// \sa <A HREF="http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf">Recommendation
///   for Random Number Generation Using Deterministic Random Bit Generators, Rev 1 (June 2015)</A>
/// \since Crypto++ 6.0
template <typename HASH=SHA256, unsigned int STRENGTH=128/8, unsigned int SEEDLENGTH=440/8>
class Hash_DRBG : public NIST_DRBG, public NotCopyable
{
public:
    CRYPTOPP_CONSTANT(SECURITY_STRENGTH=STRENGTH)
    CRYPTOPP_CONSTANT(SEED_LENGTH=SEEDLENGTH)
    CRYPTOPP_CONSTANT(MINIMUM_ENTROPY=STRENGTH)
    CRYPTOPP_CONSTANT(MINIMUM_NONCE=0)
    CRYPTOPP_CONSTANT(MINIMUM_ADDITIONAL=0)
    CRYPTOPP_CONSTANT(MINIMUM_PERSONALIZATION=0)
    CRYPTOPP_CONSTANT(MAXIMUM_ENTROPY=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_NONCE=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_ADDITIONAL=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_PERSONALIZATION=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_BYTES_PER_REQUEST=65536)
    CRYPTOPP_CONSTANT(MAXIMUM_REQUESTS_BEFORE_RESEED=INT_MAX)

    static std::string StaticAlgorithmName() { return std::string("Hash_DRBG(") + HASH::StaticAlgorithmName() + std::string(")"); }

    /// \brief Construct a Hash DRBG
    /// \param entropy the entropy to instantiate the generator
    /// \param entropyLength the size of the entropy buffer
    /// \param nonce additional input to instantiate the generator
    /// \param nonceLength the size of the nonce buffer
    /// \param personalization additional input to instantiate the generator
    /// \param personalizationLength the size of the personalization buffer
    /// \throws NIST_DRBG::Err if the generator is instantiated with insufficient entropy
    /// \details All NIST DRBGs must be instaniated with at least <tt>MINIMUM_ENTROPY</tt> bytes of entropy.
    ///   The byte array for <tt>entropy</tt> must meet <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST
    ///   SP 800-90B or SP 800-90C</A> requirements.
    /// \details The <tt>nonce</tt> and <tt>personalization</tt> are optional byte arrays. If <tt>nonce</tt> is supplied,
    ///   then it should be at least <tt>MINIMUM_NONCE</tt> bytes of entropy.
    /// \details An example of instantiating a SHA256 generator is shown below.
    ///   The example provides more entropy than required for SHA256. The <tt>NonblockingRng</tt> meets the
    ///   requirements of <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or SP 800-90C</A>.
    ///   RDRAND() and RDSEED() generators would work as well.
    /// <pre>
    ///    SecByteBlock entropy(48), result(128);
    ///    NonblockingRng prng;
    ///    RandomNumberSource rns(prng, entropy.size(), new ArraySink(entropy, entropy.size()));
    ///
    ///    Hash_DRBG<SHA256, 128/8, 440/8> drbg(entropy, 32, entropy+32, 16);
    ///    drbg.GenerateBlock(result, result.size());
    /// </pre>
    Hash_DRBG(const byte* entropy=NULLPTR, size_t entropyLength=STRENGTH, const byte* nonce=NULLPTR,
        size_t nonceLength=0, const byte* personalization=NULLPTR, size_t personalizationLength=0)
        : NIST_DRBG(), m_c(SEEDLENGTH), m_v(SEEDLENGTH), m_reseed(0)
    {
        if (entropy != NULLPTR && entropyLength != 0)
            DRBG_Instantiate(entropy, entropyLength, nonce, nonceLength, personalization, personalizationLength);
    }

    unsigned int SecurityStrength() const {return SECURITY_STRENGTH;}
    unsigned int SeedLength() const {return SEED_LENGTH;}
    unsigned int MinEntropyLength() const {return MINIMUM_ENTROPY;}
    unsigned int MaxEntropyLength() const {return MAXIMUM_ENTROPY;}
    unsigned int MinNonceLength() const {return MINIMUM_NONCE;}
    unsigned int MaxNonceLength() const {return MAXIMUM_NONCE;}
    unsigned int MaxBytesPerRequest() const {return MAXIMUM_BYTES_PER_REQUEST;}
    unsigned int MaxRequestBeforeReseed() const {return MAXIMUM_REQUESTS_BEFORE_RESEED;}

    void IncorporateEntropy(const byte *input, size_t length)
        {return DRBG_Reseed(input, length, NULLPTR, 0);}

    void IncorporateEntropy(const byte *entropy, size_t entropyLength, const byte* additional, size_t additionaLength)
        {return DRBG_Reseed(entropy, entropyLength, additional, additionaLength);}

    void GenerateBlock(byte *output, size_t size)
        {return Hash_Generate(NULLPTR, 0, output, size);}

    void GenerateBlock(const byte* additional, size_t additionaLength, byte *output, size_t size)
        {return Hash_Generate(additional, additionaLength, output, size);}

    std::string AlgorithmProvider() const
        {/*Hack*/HASH hash; return hash.AlgorithmProvider();}

protected:
    // 10.1.1.2 Instantiation of Hash_DRBG (p.39)
    void DRBG_Instantiate(const byte* entropy, size_t entropyLength, const byte* nonce, size_t nonceLength,
        const byte* personalization, size_t personalizationLength);

    // 10.1.1.3 Reseeding a Hash_DRBG Instantiation (p.40)
    void DRBG_Reseed(const byte* entropy, size_t entropyLength, const byte* additional, size_t additionaLength);

    // 10.1.1.4 Generating Pseudorandom Bits Using Hash_DRBG (p.41)
    void Hash_Generate(const byte* additional, size_t additionaLength, byte *output, size_t size);

    // 10.3.1 Derivation Function Using a Hash Function (Hash_df) (p.49)
    void Hash_Update(const byte* input1, size_t inlen1, const byte* input2, size_t inlen2,
        const byte* input3, size_t inlen3, const byte* input4, size_t inlen4, byte* output, size_t outlen);

private:
    HASH m_hash;
    SecByteBlock m_c, m_v, m_temp;
    word64 m_reseed;
};

// typedef Hash_DRBG<SHA1,   128/8, 440/8> Hash_SHA1_DRBG;
// typedef Hash_DRBG<SHA256, 128/8, 440/8> Hash_SHA256_DRBG;
// typedef Hash_DRBG<SHA384, 256/8, 888/8> Hash_SHA384_DRBG;
// typedef Hash_DRBG<SHA512, 256/8, 888/8> Hash_SHA512_DRBG;

// *************************************************************

/// \tparam HASH NIST approved hash derived from HashTransformation
/// \tparam STRENGTH security strength, in bytes
/// \tparam SEEDLENGTH seed length, in bytes
/// \brief HMAC_DRBG from SP 800-90A Rev 1 (June 2015)
/// \details The NIST HMAC DRBG is instantiated with a number of parameters. Two of the parameters,
///   Security Strength and Seed Length, depend on the hash and are specified as template parameters.
///   The remaining parameters are included in the class. The parameters and their values are listed
///   in NIST SP 800-90A Rev. 1, Table 2: Definitions for Hash-Based DRBG Mechanisms (p.38).
/// \details Some parameters have been reduce to fit C++ datatypes. For example, NIST allows upto 2<sup>48</sup> requests
///   before a reseed. However, HMAC_DRBG limits it to <tt>INT_MAX</tt> due to the limited data range of an int.
/// \sa <A HREF="http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf">Recommendation
///   for Random Number Generation Using Deterministic Random Bit Generators, Rev 1 (June 2015)</A>
/// \since Crypto++ 6.0
template <typename HASH=SHA256, unsigned int STRENGTH=128/8, unsigned int SEEDLENGTH=440/8>
class HMAC_DRBG : public NIST_DRBG, public NotCopyable
{
public:
    CRYPTOPP_CONSTANT(SECURITY_STRENGTH=STRENGTH)
    CRYPTOPP_CONSTANT(SEED_LENGTH=SEEDLENGTH)
    CRYPTOPP_CONSTANT(MINIMUM_ENTROPY=STRENGTH)
    CRYPTOPP_CONSTANT(MINIMUM_NONCE=0)
    CRYPTOPP_CONSTANT(MINIMUM_ADDITIONAL=0)
    CRYPTOPP_CONSTANT(MINIMUM_PERSONALIZATION=0)
    CRYPTOPP_CONSTANT(MAXIMUM_ENTROPY=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_NONCE=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_ADDITIONAL=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_PERSONALIZATION=INT_MAX)
    CRYPTOPP_CONSTANT(MAXIMUM_BYTES_PER_REQUEST=65536)
    CRYPTOPP_CONSTANT(MAXIMUM_REQUESTS_BEFORE_RESEED=INT_MAX)

    static std::string StaticAlgorithmName() { return std::string("HMAC_DRBG(") + HASH::StaticAlgorithmName() + std::string(")"); }

    /// \brief Construct a HMAC DRBG
    /// \param entropy the entropy to instantiate the generator
    /// \param entropyLength the size of the entropy buffer
    /// \param nonce additional input to instantiate the generator
    /// \param nonceLength the size of the nonce buffer
    /// \param personalization additional input to instantiate the generator
    /// \param personalizationLength the size of the personalization buffer
    /// \throws NIST_DRBG::Err if the generator is instantiated with insufficient entropy
    /// \details All NIST DRBGs must be instaniated with at least <tt>MINIMUM_ENTROPY</tt> bytes of entropy.
    ///   The byte array for <tt>entropy</tt> must meet <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST
    ///   SP 800-90B or SP 800-90C</A> requirements.
    /// \details The <tt>nonce</tt> and <tt>personalization</tt> are optional byte arrays. If <tt>nonce</tt> is supplied,
    ///   then it should be at least <tt>MINIMUM_NONCE</tt> bytes of entropy.
    /// \details An example of instantiating a SHA256 generator is shown below.
    ///   The example provides more entropy than required for SHA256. The <tt>NonblockingRng</tt> meets the
    ///   requirements of <A HREF ="http://csrc.nist.gov/publications/PubsSPs.html">NIST SP 800-90B or SP 800-90C</A>.
    ///   RDRAND() and RDSEED() generators would work as well.
    /// <pre>
    ///    SecByteBlock entropy(48), result(128);
    ///    NonblockingRng prng;
    ///    RandomNumberSource rns(prng, entropy.size(), new ArraySink(entropy, entropy.size()));
    ///
    ///    HMAC_DRBG<SHA256, 128/8, 440/8> drbg(entropy, 32, entropy+32, 16);
    ///    drbg.GenerateBlock(result, result.size());
    /// </pre>
    HMAC_DRBG(const byte* entropy=NULLPTR, size_t entropyLength=STRENGTH, const byte* nonce=NULLPTR,
        size_t nonceLength=0, const byte* personalization=NULLPTR, size_t personalizationLength=0)
        : NIST_DRBG(), m_k(HASH::DIGESTSIZE), m_v(HASH::DIGESTSIZE), m_reseed(0)
    {
        if (entropy != NULLPTR && entropyLength != 0)
            DRBG_Instantiate(entropy, entropyLength, nonce, nonceLength, personalization, personalizationLength);
    }

    unsigned int SecurityStrength() const {return SECURITY_STRENGTH;}
    unsigned int SeedLength() const {return SEED_LENGTH;}
    unsigned int MinEntropyLength() const {return MINIMUM_ENTROPY;}
    unsigned int MaxEntropyLength() const {return MAXIMUM_ENTROPY;}
    unsigned int MinNonceLength() const {return MINIMUM_NONCE;}
    unsigned int MaxNonceLength() const {return MAXIMUM_NONCE;}
    unsigned int MaxBytesPerRequest() const {return MAXIMUM_BYTES_PER_REQUEST;}
    unsigned int MaxRequestBeforeReseed() const {return MAXIMUM_REQUESTS_BEFORE_RESEED;}

    void IncorporateEntropy(const byte *input, size_t length)
        {return DRBG_Reseed(input, length, NULLPTR, 0);}

    void IncorporateEntropy(const byte *entropy, size_t entropyLength, const byte* additional, size_t additionaLength)
        {return DRBG_Reseed(entropy, entropyLength, additional, additionaLength);}

    void GenerateBlock(byte *output, size_t size)
        {return HMAC_Generate(NULLPTR, 0, output, size);}

    void GenerateBlock(const byte* additional, size_t additionaLength, byte *output, size_t size)
        {return HMAC_Generate(additional, additionaLength, output, size);}

    std::string AlgorithmProvider() const
        {/*Hack*/HASH hash; return hash.AlgorithmProvider();}

protected:
    // 10.1.2.3 Instantiation of HMAC_DRBG (p.45)
    void DRBG_Instantiate(const byte* entropy, size_t entropyLength, const byte* nonce, size_t nonceLength,
        const byte* personalization, size_t personalizationLength);

    // 10.1.2.4 Reseeding a HMAC_DRBG Instantiation (p.46)
    void DRBG_Reseed(const byte* entropy, size_t entropyLength, const byte* additional, size_t additionaLength);

    // 10.1.2.5 Generating Pseudorandom Bits Using HMAC_DRBG (p.46)
    void HMAC_Generate(const byte* additional, size_t additionaLength, byte *output, size_t size);

    // 10.1.2.2 Derivation Function Using a HMAC Function (HMAC_Update) (p.44)
    void HMAC_Update(const byte* input1, size_t inlen1, const byte* input2, size_t inlen2, const byte* input3, size_t inlen3);

private:
    HMAC<HASH> m_hmac;
    SecByteBlock m_k, m_v;
    word64 m_reseed;
};

// typedef HMAC_DRBG<SHA1,   128/8, 440/8> HMAC_SHA1_DRBG;
// typedef HMAC_DRBG<SHA256, 128/8, 440/8> HMAC_SHA256_DRBG;
// typedef HMAC_DRBG<SHA384, 256/8, 888/8> HMAC_SHA384_DRBG;
// typedef HMAC_DRBG<SHA512, 256/8, 888/8> HMAC_SHA512_DRBG;

// *************************************************************

// 10.1.1.2 Instantiation of Hash_DRBG (p.39)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void Hash_DRBG<HASH, STRENGTH, SEEDLENGTH>::DRBG_Instantiate(const byte* entropy, size_t entropyLength, const byte* nonce, size_t nonceLength,
    const byte* personalization, size_t personalizationLength)
{
    //  SP 800-90A, 8.6.3: The entropy input shall have entropy that is equal to or greater than the security
    //  strength of the instantiation. Additional entropy may be provided in the nonce or the optional
    //  personalization string during instantiation, or in the additional input during reseeding and generation,
    //  but this is not required and does not increase the "official" security strength of the DRBG
    //  instantiation that is recorded in the internal state.
    CRYPTOPP_ASSERT(entropyLength >= MINIMUM_ENTROPY);
    if (entropyLength < MINIMUM_ENTROPY)
        throw NIST_DRBG::Err("Hash_DRBG", "Insufficient entropy during instantiate");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(entropyLength <= MAXIMUM_ENTROPY);
    CRYPTOPP_ASSERT(nonceLength <= MAXIMUM_NONCE);
    CRYPTOPP_ASSERT(personalizationLength <= MAXIMUM_PERSONALIZATION);

    const byte zero = 0;
    SecByteBlock t1(SEEDLENGTH), t2(SEEDLENGTH);
    Hash_Update(entropy, entropyLength, nonce, nonceLength, personalization, personalizationLength, NULLPTR, 0, t1, t1.size());
    Hash_Update(&zero, 1, t1, t1.size(), NULLPTR, 0, NULLPTR, 0, t2, t2.size());

    m_v.swap(t1); m_c.swap(t2);
    m_reseed = 1;
}

// 10.1.1.3 Reseeding a Hash_DRBG Instantiation (p.40)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void Hash_DRBG<HASH, STRENGTH, SEEDLENGTH>::DRBG_Reseed(const byte* entropy, size_t entropyLength, const byte* additional, size_t additionaLength)
{
    //  SP 800-90A, 8.6.3: The entropy input shall have entropy that is equal to or greater than the security
    //  strength of the instantiation. Additional entropy may be provided in the nonce or the optional
    //  personalization string during instantiation, or in the additional input during reseeding and generation,
    //  but this is not required and does not increase the "official" security strength of the DRBG
    //  instantiation that is recorded in the internal state..
    CRYPTOPP_ASSERT(entropyLength >= MINIMUM_ENTROPY);
    if (entropyLength < MINIMUM_ENTROPY)
        throw NIST_DRBG::Err("Hash_DRBG", "Insufficient entropy during reseed");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(entropyLength <= MAXIMUM_ENTROPY);
    CRYPTOPP_ASSERT(additionaLength <= MAXIMUM_ADDITIONAL);

    const byte zero = 0, one = 1;
    SecByteBlock t1(SEEDLENGTH), t2(SEEDLENGTH);
    Hash_Update(&one, 1, m_v, m_v.size(), entropy, entropyLength, additional, additionaLength, t1, t1.size());
    Hash_Update(&zero, 1, t1, t1.size(), NULLPTR, 0, NULLPTR, 0, t2, t2.size());

    m_v.swap(t1); m_c.swap(t2);
    m_reseed = 1;
}

// 10.1.1.4 Generating Pseudorandom Bits Using Hash_DRBG (p.41)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void Hash_DRBG<HASH, STRENGTH, SEEDLENGTH>::Hash_Generate(const byte* additional, size_t additionaLength, byte *output, size_t size)
{
    // Step 1
    if (static_cast<word64>(m_reseed) >= static_cast<word64>(MaxRequestBeforeReseed()))
        throw NIST_DRBG::Err("Hash_DRBG", "Reseed required");

    if (size > MaxBytesPerRequest())
        throw NIST_DRBG::Err("Hash_DRBG", "Request size exceeds limit");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(additionaLength <= MAXIMUM_ADDITIONAL);

    // Step 2
    if (additional && additionaLength)
    {
        const byte two = 2;
        m_temp.New(HASH::DIGESTSIZE);

        m_hash.Update(&two, 1);
        m_hash.Update(m_v, m_v.size());
        m_hash.Update(additional, additionaLength);
        m_hash.Final(m_temp);

        CRYPTOPP_ASSERT(SEEDLENGTH >= HASH::DIGESTSIZE);
        int carry=0, j=HASH::DIGESTSIZE-1, i=SEEDLENGTH-1;
        while (j>=0)
        {
            carry = m_v[i] + m_temp[j] + carry;
            m_v[i] = static_cast<byte>(carry);
            i--; j--; carry >>= 8;
        }
        while (i>=0)
        {
            carry = m_v[i] + carry;
            m_v[i] = static_cast<byte>(carry);
            i--; carry >>= 8;
        }
    }

    // Step 3
    {
        m_temp.Assign(m_v);
        while (size)
        {
            m_hash.Update(m_temp, m_temp.size());
            size_t count = STDMIN(size, (size_t)HASH::DIGESTSIZE);
            m_hash.TruncatedFinal(output, count);

            IncrementCounterByOne(m_temp, static_cast<unsigned int>(m_temp.size()));
            size -= count; output += count;
        }
    }

    // Steps 4-7
    {
        const byte three = 3;
        m_temp.New(HASH::DIGESTSIZE);

        m_hash.Update(&three, 1);
        m_hash.Update(m_v, m_v.size());
        m_hash.Final(m_temp);

        CRYPTOPP_ASSERT(SEEDLENGTH >= HASH::DIGESTSIZE);
        CRYPTOPP_ASSERT(HASH::DIGESTSIZE >= sizeof(m_reseed));
        int carry=0, k=sizeof(m_reseed)-1, j=HASH::DIGESTSIZE-1, i=SEEDLENGTH-1;

        while (k>=0)
        {
            carry = m_v[i] + m_c[i] + m_temp[j] + GetByte<word64>(BIG_ENDIAN_ORDER, m_reseed, k) + carry;
            m_v[i] = static_cast<byte>(carry);
            i--; j--; k--; carry >>= 8;
        }

        while (j>=0)
        {
            carry = m_v[i] + m_c[i] + m_temp[j] + carry;
            m_v[i] = static_cast<byte>(carry);
            i--; j--; carry >>= 8;
        }

        while (i>=0)
        {
            carry = m_v[i] + m_c[i] + carry;
            m_v[i] = static_cast<byte>(carry);
            i--; carry >>= 8;
        }
    }

    m_reseed++;
}

// 10.3.1 Derivation Function Using a Hash Function (Hash_df) (p.49)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void Hash_DRBG<HASH, STRENGTH, SEEDLENGTH>::Hash_Update(const byte* input1, size_t inlen1, const byte* input2, size_t inlen2,
    const byte* input3, size_t inlen3, const byte* input4, size_t inlen4, byte* output, size_t outlen)
{
    byte counter = 1;
    word32 bits = ConditionalByteReverse(BIG_ENDIAN_ORDER, static_cast<word32>(outlen*8));

    while (outlen)
    {
        m_hash.Update(&counter, 1);
        m_hash.Update(reinterpret_cast<const byte*>(&bits), 4);

        if (input1 && inlen1)
            m_hash.Update(input1, inlen1);
        if (input2 && inlen2)
            m_hash.Update(input2, inlen2);
        if (input3 && inlen3)
            m_hash.Update(input3, inlen3);
        if (input4 && inlen4)
            m_hash.Update(input4, inlen4);

        size_t count = STDMIN(outlen, (size_t)HASH::DIGESTSIZE);
        m_hash.TruncatedFinal(output, count);

        output += count; outlen -= count;
        counter++;
    }
}

// *************************************************************

// 10.1.2.3 Instantiation of HMAC_DRBG (p.45)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void HMAC_DRBG<HASH, STRENGTH, SEEDLENGTH>::DRBG_Instantiate(const byte* entropy, size_t entropyLength, const byte* nonce, size_t nonceLength,
    const byte* personalization, size_t personalizationLength)
{
    //  SP 800-90A, 8.6.3: The entropy input shall have entropy that is equal to or greater than the security
    //  strength of the instantiation. Additional entropy may be provided in the nonce or the optional
    //  personalization string during instantiation, or in the additional input during reseeding and generation,
    //  but this is not required and does not increase the "official" security strength of the DRBG
    //  instantiation that is recorded in the internal state.
    CRYPTOPP_ASSERT(entropyLength >= MINIMUM_ENTROPY);
    if (entropyLength < MINIMUM_ENTROPY)
        throw NIST_DRBG::Err("HMAC_DRBG", "Insufficient entropy during instantiate");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(entropyLength <= MAXIMUM_ENTROPY);
    CRYPTOPP_ASSERT(nonceLength <= MAXIMUM_NONCE);
    CRYPTOPP_ASSERT(personalizationLength <= MAXIMUM_PERSONALIZATION);

    std::fill(m_k.begin(), m_k.begin()+m_k.size(), byte(0));
    std::fill(m_v.begin(), m_v.begin()+m_v.size(), byte(1));

    HMAC_Update(entropy, entropyLength, nonce, nonceLength, personalization, personalizationLength);
    m_reseed = 1;
}

// 10.1.2.4 Reseeding a HMAC_DRBG Instantiation (p.46)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void HMAC_DRBG<HASH, STRENGTH, SEEDLENGTH>::DRBG_Reseed(const byte* entropy, size_t entropyLength, const byte* additional, size_t additionaLength)
{
    //  SP 800-90A, 8.6.3: The entropy input shall have entropy that is equal to or greater than the security
    //  strength of the instantiation. Additional entropy may be provided in the nonce or the optional
    //  personalization string during instantiation, or in the additional input during reseeding and generation,
    //  but this is not required and does not increase the "official" security strength of the DRBG
    //  instantiation that is recorded in the internal state..
    CRYPTOPP_ASSERT(entropyLength >= MINIMUM_ENTROPY);
    if (entropyLength < MINIMUM_ENTROPY)
        throw NIST_DRBG::Err("HMAC_DRBG", "Insufficient entropy during reseed");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(entropyLength <= MAXIMUM_ENTROPY);
    CRYPTOPP_ASSERT(additionaLength <= MAXIMUM_ADDITIONAL);

    HMAC_Update(entropy, entropyLength, additional, additionaLength, NULLPTR, 0);
    m_reseed = 1;
}

// 10.1.2.5 Generating Pseudorandom Bits Using HMAC_DRBG (p.46)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void HMAC_DRBG<HASH, STRENGTH, SEEDLENGTH>::HMAC_Generate(const byte* additional, size_t additionaLength, byte *output, size_t size)
{
    // Step 1
    if (static_cast<word64>(m_reseed) >= static_cast<word64>(MaxRequestBeforeReseed()))
        throw NIST_DRBG::Err("HMAC_DRBG", "Reseed required");

    if (size > MaxBytesPerRequest())
        throw NIST_DRBG::Err("HMAC_DRBG", "Request size exceeds limit");

    // SP 800-90A, Section 9, says we should throw if we have too much entropy, too large a nonce,
    // or too large a persoanlization string. We warn in Debug builds, but do nothing in Release builds.
    CRYPTOPP_ASSERT(additionaLength <= MAXIMUM_ADDITIONAL);

    // Step 2
    if (additional && additionaLength)
        HMAC_Update(additional, additionaLength, NULLPTR, 0, NULLPTR, 0);

    // Step 3
    m_hmac.SetKey(m_k, m_k.size());

    while (size)
    {
        m_hmac.Update(m_v, m_v.size());
        m_hmac.TruncatedFinal(m_v, m_v.size());

        size_t count = STDMIN(size, (size_t)HASH::DIGESTSIZE);
        memcpy(output, m_v, count);
        size -= count; output += count;
    }

    HMAC_Update(additional, additionaLength, NULLPTR, 0, NULLPTR, 0);
    m_reseed++;
}

// 10.1.2.2 Derivation Function Using a HMAC Function (HMAC_Update) (p.44)
template <typename HASH, unsigned int STRENGTH, unsigned int SEEDLENGTH>
void HMAC_DRBG<HASH, STRENGTH, SEEDLENGTH>::HMAC_Update(const byte* input1, size_t inlen1, const byte* input2, size_t inlen2, const byte* input3, size_t inlen3)
{
    const byte zero = 0, one = 1;

    // Step 1
    m_hmac.SetKey(m_k, m_k.size());
    m_hmac.Update(m_v, m_v.size());
    m_hmac.Update(&zero, 1);

    if (input1 && inlen1)
        m_hmac.Update(input1, inlen1);
    if (input2 && inlen2)
        m_hmac.Update(input2, inlen2);
    if (input3 && inlen3)
        m_hmac.Update(input3, inlen3);

    m_hmac.TruncatedFinal(m_k, m_k.size());

    // Step 2
    m_hmac.SetKey(m_k, m_k.size());
    m_hmac.Update(m_v, m_v.size());

    m_hmac.TruncatedFinal(m_v, m_v.size());

    // Step 3
    if ((inlen1 | inlen2 | inlen3) == 0)
        return;

    // Step 4
    m_hmac.SetKey(m_k, m_k.size());
    m_hmac.Update(m_v, m_v.size());
    m_hmac.Update(&one, 1);

    if (input1 && inlen1)
        m_hmac.Update(input1, inlen1);
    if (input2 && inlen2)
        m_hmac.Update(input2, inlen2);
    if (input3 && inlen3)
        m_hmac.Update(input3, inlen3);

    m_hmac.TruncatedFinal(m_k, m_k.size());

    // Step 5
    m_hmac.SetKey(m_k, m_k.size());
    m_hmac.Update(m_v, m_v.size());

    m_hmac.TruncatedFinal(m_v, m_v.size());
}

NAMESPACE_END

#endif  // CRYPTOPP_NIST_DRBG_H