(Excel) 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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' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2

' 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 To 9

    counterHex = crypt.EncodeInt(count,8,False,"hex")

    hotp = crypt.Hotp(secret,"ascii",counterHex,6,-1,"sha1")
    Debug.Print count; "  HOTP = "; hotp
Next

' 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