(C) HOTP Algorithm: HMAC-Based One-Time Password Algorithm

Demonstrates how to generate an HMAC one-time password (HOTP) as specified in RFC 4226.

Note: This example requires Chilkat v9.5.0.77 or greater.

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#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    const char *secret;
    int count;
    const char *counterHex;
    const char *hotp;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    crypt = CkCrypt2_Create();

    // Duplicate the following results from RFC 4226

    // Appendix D - HOTP Algorithm: Test Values
    // 
    //   The following test data uses the ASCII string
    //   "12345678901234567890" for the secret:
    // 
    //   Secret = 0x3132333435363738393031323334353637383930
    // 
    //                     Truncated
    //   Count    Hexadecimal    Decimal        HOTP
    //   0        4c93cf18       1284755224     755224
    //   1        41397eea       1094287082     287082
    //   2         82fef30        137359152     359152
    //   3        66ef7655       1726969429     969429
    //   4        61c5938a       1640338314     338314
    //   5        33c083d4        868254676     254676
    //   6        7256c032       1918287922     287922
    //   7         4e5b397         82162583     162583
    //   8        2823443f        673399871     399871
    //   9        2679dc69        645520489     520489

    secret = "12345678901234567890";

    for (count = 0; count <= 9; count++) {
        counterHex = CkCrypt2_encodeInt(crypt,count,8,FALSE,"hex");
        hotp = CkCrypt2_hotp(crypt,secret,"ascii",counterHex,6,-1,"sha1");
        printf("%d  HOTP = %s\n",count,hotp);
    }

    // Output is:
    // 0  HOTP = 755224
    // 1  HOTP = 287082
    // 2  HOTP = 359152
    // 3  HOTP = 969429
    // 4  HOTP = 338314
    // 5  HOTP = 254676
    // 6  HOTP = 287922
    // 7  HOTP = 162583
    // 8  HOTP = 399871
    // 9  HOTP = 520489


    CkCrypt2_Dispose(crypt);

    }