Criptografie (1) - Algoritmului SHA-256

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Descrierea algoritmului SHA-256

 SHA-256 aparține familiei de funcții hash criptografice SHA-2 proiectate de NSA și este utilizată în mod obișnuit în Blockchain.

SHA, care înseamnă algoritm securizat de hash, este un algoritm de hash criptografic utilizat pentru a determina integritatea unei anumite date. SHA-256  este în prezent mult mai rezistent la atacurile de coliziune, deoarece este capabil să genereze un hash mai lung, care este mai greu de spart.

O funcție hash ia un șir arbitrar ca intrare, iar intrarea este denumită în mod obișnuit „mesaj”. Funția produce o ieșire care are o lungime FIXĂ, adică  SHA-256 produce un șir de 256 de biți (32 bytes) . Ieșirea se numește în mod obișnuit „Mesaj Digest” sau „Valoare Hash” sau doar „Hash”. Ieșirile funcției hash vor fi numite H(x) , și algoritmul său se termină într-un timp rezonabil. În mod normal este util să comparăm două mesaje pentru egalitate, și dacă nu știm mesajele în sine, atunci putem spune dacă H (x) = H (y), de asemenea "mesajul x" = "mesajul y".

La un nivel înalt, SHA-256 funcționează astfel: 

  1.  Luați mesajul de intrare și asigurați-vă că lungimea acestuia (în biți) este un multiplu de 512 biți. Acest lucru se face prin adăugarea unor biți de padding.
  2.   Luați mesajul transmis și analizați-l în blocuri de N 512 biți. 
  3.   Repetați toate blocurile de la pasul 2: 
  1.  Inițializați programarea mesajelor, o secvență de 64 words pe 32 de biți 
  2.  Inițializați opt variabile de lucru a ... h cu valorile hash H0 ... H7 din iterația anterioară (pentru prima iterație, H0 ... H7 sunt inițializate cu constante).  
  3. Efectuați 64 de iterații în care variabilele de lucru a ... h sunt rotite într-un anumit mod. Aceasta este inima funcției hash. În acest pas, mesajul este introdus în hash folosind o mulțime de amestecuri pe biți.   
  4. Calculați noile valori hash intermediare H0 ... H7 ca H0 = H0 + a, H1 = H1 + b și așa mai departe. 
     4. Concatenează H0 ... H7 ca mesaj de rezumat și returnează-l.

Descrierea algoritmului SHA-256

Descrierea algoritmului SHA-256
Descrierea algoritmului SHA-256

 
Descrierea algoritmului SHA-256

Descrierea algoritmului SHA-256
Descrierea algoritmului SHA-256


Documentatie:

 Compilator:

Implementări:

Teste: 

Am folosit librăria TinyCrypt pentru teste și am listat și rezultele mai jos. 



/*  test_sha256.c - TinyCrypt implementation of some SHA-256 tests */

/*
 *  Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
 *
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 *  modification, are permitted provided that the following conditions are met:
 *
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 *     this list of conditions and the following disclaimer.
 *
 *    - Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *    - Neither the name of Intel Corporation nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/*
  DESCRIPTION
  This module tests the following SHA256 routines:

  Scenarios tested include:
  - NIST SHA256 test vectors
*/

#include "sha256.h"
#include "constants.h"
#include "test_utils.h"

#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "stdint.h"

/*
 * NIST SHA256 test vector 1.
 */
unsigned int test_1(void)
{
        unsigned int result = TC_PASS;

        TC_PRINT("SHA256 test #1:\n");
        const uint8_t expected[32] = {
		0xba, 0x78, 0x16, 0xbf, 0x8f, 0x01, 0xcf, 0xea, 0x41, 0x41, 0x40, 0xde,
		0x5d, 0xae, 0x22, 0x23, 0xb0, 0x03, 0x61, 0xa3, 0x96, 0x17, 0x7a, 0x9c,
		0xb4, 0x10, 0xff, 0x61, 0xf2, 0x00, 0x15, 0xad
        };
        const char *m = "abc";
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, (const uint8_t *) m, strlen(m));
        (void)tc_sha256_final(digest, &s);
        result = check_result(1, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

/*
 * NIST SHA256 test vector 2.
 */
unsigned int test_2(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #2:\n");
        const uint8_t expected[32] = {
		0x24, 0x8d, 0x6a, 0x61, 0xd2, 0x06, 0x38, 0xb8, 0xe5, 0xc0, 0x26, 0x93,
		0x0c, 0x3e, 0x60, 0x39, 0xa3, 0x3c, 0xe4, 0x59, 0x64, 0xff, 0x21, 0x67,
		0xf6, 0xec, 0xed, 0xd4, 0x19, 0xdb, 0x06, 0xc1
        };
        const char *m = "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq";
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, (const uint8_t *) m, strlen(m));
        (void) tc_sha256_final(digest, &s);

        result = check_result(2, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_3(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #3:\n");
        const uint8_t expected[32] = {
		0x68, 0x32, 0x57, 0x20, 0xaa, 0xbd, 0x7c, 0x82, 0xf3, 0x0f, 0x55, 0x4b,
		0x31, 0x3d, 0x05, 0x70, 0xc9, 0x5a, 0xcc, 0xbb, 0x7d, 0xc4, 0xb5, 0xaa,
		0xe1, 0x12, 0x04, 0xc0, 0x8f, 0xfe, 0x73, 0x2b
        };
        const uint8_t m[1] = { 0xbd };
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(3, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_4(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #4:\n");
        const uint8_t expected[32] = {
		0x7a, 0xbc, 0x22, 0xc0, 0xae, 0x5a, 0xf2, 0x6c, 0xe9, 0x3d, 0xbb, 0x94,
		0x43, 0x3a, 0x0e, 0x0b, 0x2e, 0x11, 0x9d, 0x01, 0x4f, 0x8e, 0x7f, 0x65,
		0xbd, 0x56, 0xc6, 0x1c, 0xcc, 0xcd, 0x95, 0x04
        };
        const uint8_t m[4] = { 0xc9, 0x8c, 0x8e, 0x55 };
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(4, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_5(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #5:\n");

        const uint8_t expected[32] = {
		0x02, 0x77, 0x94, 0x66, 0xcd, 0xec, 0x16, 0x38, 0x11, 0xd0, 0x78, 0x81,
		0x5c, 0x63, 0x3f, 0x21, 0x90, 0x14, 0x13, 0x08, 0x14, 0x49, 0x00, 0x2f,
		0x24, 0xaa, 0x3e, 0x80, 0xf0, 0xb8, 0x8e, 0xf7
        };
        uint8_t m[55];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(5, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_6(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #6:\n");
        const uint8_t expected[32] = {
		0xd4, 0x81, 0x7a, 0xa5, 0x49, 0x76, 0x28, 0xe7, 0xc7, 0x7e, 0x6b, 0x60,
		0x61, 0x07, 0x04, 0x2b, 0xbb, 0xa3, 0x13, 0x08, 0x88, 0xc5, 0xf4, 0x7a,
		0x37, 0x5e, 0x61, 0x79, 0xbe, 0x78, 0x9f, 0xbb
        };
        uint8_t m[56];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(6, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_7(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #7:\n");
        const uint8_t expected[32] = {
		0x65, 0xa1, 0x6c, 0xb7, 0x86, 0x13, 0x35, 0xd5, 0xac, 0xe3, 0xc6, 0x07,
		0x18, 0xb5, 0x05, 0x2e, 0x44, 0x66, 0x07, 0x26, 0xda, 0x4c, 0xd1, 0x3b,
		0xb7, 0x45, 0x38, 0x1b, 0x23, 0x5a, 0x17, 0x85
        };
        uint8_t m[57];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(7, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_8(void)
{
        unsigned int result = TC_PASS;

        TC_PRINT("SHA256 test #8:\n");
        const uint8_t expected[32] = {
		0xf5, 0xa5, 0xfd, 0x42, 0xd1, 0x6a, 0x20, 0x30, 0x27, 0x98, 0xef, 0x6e,
		0xd3, 0x09, 0x97, 0x9b, 0x43, 0x00, 0x3d, 0x23, 0x20, 0xd9, 0xf0, 0xe8,
		0xea, 0x98, 0x31, 0xa9, 0x27, 0x59, 0xfb, 0x4b
        };
        uint8_t m[64];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(8, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_9(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #9:\n");
        const uint8_t expected[32] = {
		0x54, 0x1b, 0x3e, 0x9d, 0xaa, 0x09, 0xb2, 0x0b, 0xf8, 0x5f, 0xa2, 0x73,
		0xe5, 0xcb, 0xd3, 0xe8, 0x01, 0x85, 0xaa, 0x4e, 0xc2, 0x98, 0xe7, 0x65,
		0xdb, 0x87, 0x74, 0x2b, 0x70, 0x13, 0x8a, 0x53
        };
        uint8_t m[1000];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(9, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_10(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #10:\n");
        const uint8_t expected[32] = {
		0xc2, 0xe6, 0x86, 0x82, 0x34, 0x89, 0xce, 0xd2, 0x01, 0x7f, 0x60, 0x59,
		0xb8, 0xb2, 0x39, 0x31, 0x8b, 0x63, 0x64, 0xf6, 0xdc, 0xd8, 0x35, 0xd0,
		0xa5, 0x19, 0x10, 0x5a, 0x1e, 0xad, 0xd6, 0xe4
        };
        uint8_t m[1000];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x41, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(10, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_11(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #11:\n");
        const uint8_t expected[32] = {
		0xf4, 0xd6, 0x2d, 0xde, 0xc0, 0xf3, 0xdd, 0x90, 0xea, 0x13, 0x80, 0xfa,
		0x16, 0xa5, 0xff, 0x8d, 0xc4, 0xc5, 0x4b, 0x21, 0x74, 0x06, 0x50, 0xf2,
		0x4a, 0xfc, 0x41, 0x20, 0x90, 0x35, 0x52, 0xb0
        };
        uint8_t m[1005];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)memset(m, 0x55, sizeof(m));

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, m, sizeof(m));
        (void)tc_sha256_final(digest, &s);

        result = check_result(11, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_12(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #12:\n");

        const uint8_t expected[32] = {
		0xd2, 0x97, 0x51, 0xf2, 0x64, 0x9b, 0x32, 0xff, 0x57, 0x2b, 0x5e, 0x0a,
		0x9f, 0x54, 0x1e, 0xa6, 0x60, 0xa5, 0x0f, 0x94, 0xff, 0x0b, 0xee, 0xdf,
		0xb0, 0xb6, 0x92, 0xb9, 0x24, 0xcc, 0x80, 0x25
        };
        uint8_t m[1000];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;
        unsigned int i;

        (void)memset(m, 0x00, sizeof(m));

        (void)tc_sha256_init(&s);
        for (i = 0; i < 1000; ++i) {
                tc_sha256_update(&s, m, sizeof(m));
        }
        (void)tc_sha256_final(digest, &s);

        result = check_result(12, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_13(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #13:\n");
        const uint8_t expected[32] = {
		0x15, 0xa1, 0x86, 0x8c, 0x12, 0xcc, 0x53, 0x95, 0x1e, 0x18, 0x23, 0x44,
		0x27, 0x74, 0x47, 0xcd, 0x09, 0x79, 0x53, 0x6b, 0xad, 0xcc, 0x51, 0x2a,
		0xd2, 0x4c, 0x67, 0xe9, 0xb2, 0xd4, 0xf3, 0xdd
        };
        uint8_t m[32768];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;
        unsigned int i;

        (void)memset(m, 0x5a, sizeof(m));

        (void)tc_sha256_init(&s);
        for (i = 0; i < 16384; ++i) {
                tc_sha256_update(&s, m, sizeof(m));
        }
        (void)tc_sha256_final(digest, &s);

        result = check_result(13, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_14(void)
{
        unsigned int result = TC_PASS;
        TC_PRINT("SHA256 test #14:\n");
        const uint8_t expected[32] = {
		0x46, 0x1c, 0x19, 0xa9, 0x3b, 0xd4, 0x34, 0x4f, 0x92, 0x15, 0xf5, 0xec,
		0x64, 0x35, 0x70, 0x90, 0x34, 0x2b, 0xc6, 0x6b, 0x15, 0xa1, 0x48, 0x31,
		0x7d, 0x27, 0x6e, 0x31, 0xcb, 0xc2, 0x0b, 0x53
        };
        uint8_t m[32768];
        uint8_t digest[32];
        struct tc_sha256_state_struct s;
        unsigned int i;

        (void)memset(m, 0x00, sizeof(m));

        (void) tc_sha256_init(&s);
        for (i = 0; i < 33280; ++i) {
                tc_sha256_update(&s, m, sizeof(m));
        }
        (void) tc_sha256_final(digest, &s);

        result = check_result(14, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}

unsigned int test_15(void)
{
        unsigned int result = TC_PASS;

        TC_PRINT("SHA256 test #15:\n");
        const uint8_t expected[32] = {
		0xba, 0x78, 0x16, 0xbf, 0x8f, 0x01, 0xcf, 0xea, 0x41, 0x41, 0x40, 0xde,
		0x5d, 0xae, 0x22, 0x23, 0xb0, 0x03, 0x61, 0xa3, 0x96, 0x17, 0x7a, 0x9c,
		0xb4, 0x10, 0xff, 0x61, 0xf2, 0x00, 0x15, 0xad
        };
        const char *m = "xyz";
        uint8_t digest[32];
        struct tc_sha256_state_struct s;

        (void)tc_sha256_init(&s);
        tc_sha256_update(&s, (const uint8_t *) m, strlen(m));
        (void)tc_sha256_final(digest, &s);
        result = check_result(1, expected, sizeof(expected),
			      digest, sizeof(digest));
        TC_END_RESULT(result);
        return result;
}
/*
 * Main task to test SHA256
 */

int main(void)
{
        unsigned int result = TC_PASS;
        TC_START("Performing SHA256 tests (NIST tests vectors):");

        result = test_1();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #1 failed.\n");
                goto exitTest;
        }
        result = test_2();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #2 failed.\n");
                goto exitTest;
        }
        result = test_3();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #3 failed.\n");
                goto exitTest;
        }
        result = test_4();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #4 failed.\n");
                goto exitTest;
        }
        result = test_5();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #5 failed.\n");
                goto exitTest;
        }
        result = test_6();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #6 failed.\n");
                goto exitTest;
        }
        result = test_7();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #7 failed.\n");
                goto exitTest;
        }
        result = test_8();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #8 failed.\n");
                goto exitTest;
        }
        result = test_9();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #9 failed.\n");
                goto exitTest;
        }
        result = test_10();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #10 failed.\n");
                goto exitTest;
        }
        result = test_11();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #11 failed.\n");
                goto exitTest;
        }
        result = test_12();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #12 failed.\n");
                goto exitTest;
        }
  	/* memory and computation intensive test cases: */
        result = test_13();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #13 failed.\n");
                goto exitTest;
        }
        result = test_14();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #14 failed.\n");
                goto exitTest;
        }

        result = test_15();
        if (result == TC_FAIL) {
		/* terminate test */
                TC_ERROR("SHA256 test #15 failed.\n");
                goto exitTest;
        }

exitTest:
        TC_END_RESULT(result);
        TC_END_REPORT(result);
}

Rezultat:

 Am executat testele deja implementate in librăria TinyCrypt, dar am adaugat la sfarșit un test negativ, care să evidențieze rezultatul pentru stringul "xyz".

 
 Am supra-verifica rezultatul cu un utilitar online, și pentru stringul "xyz" rezultă SHA256 HASH "3608bca1e44ea6c4d268eb6db02260269892c0b42b86bbf1e77a6fa16c3c9282", la fel ca în imaginea de mai sus.

Din curiozitate am facut si un test cu Arduino Uno folosind implementare facută de Kamaljohnson.

Am testat folosind un string empty "" si stringul meu de mai sus "xyz".

SHA256 for "xyz" is 3608bca1e44ea6c4d268eb6db02260269892c0b42b86bbf1e77a6fa16c3c9282

SHA256 for "" is e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855


 
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