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RFC 4226, "HOTP: An HMAC-Based One-Time Password Algorithm", December 2005

Source of RFC: IETF - NON WORKING GROUP
Area Assignment: sec

Errata ID: 5129

Status: Reported
Type: Technical

Reported By: Gerrit Jansen van Vuuren
Date Reported: 2017-09-27

Section Appendix D says:

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


It should say:

Count     Hexadecimal    Decimal        HOTP
   0         4c93cf18      1284755224    755224
   1         75a48a19      1973717529    717529
   2         bacb7fa       195868666     868666
   3         66c28227      1724023335    023335
   4         2904c900      688179456     179456
   5         237e783d      595490877     490877
   6         3c9cd285      1016910469    910469
   7         24fb960c      620467724     467724
   8         1b3c89f6      456952310     952310
   9         16374098      372719768     719768

Notes:

From https://www.ietf.org/rfc/rfc4226.txt, Appendix D, page 31

a. There is no mention of the parameters that were used to run the reference implementation to provide to test data. These should be:

codeDigits: 6, addCheckSum: false, truncationOffset: 0.

b. The hashes correspond. And the first row of Table2 (i.e for Count==0) correspond, but for Count 1...9 the values for Hex, Decimal and Hotp do not correspond with the values of the reference implementation.

I am using JDK 1.8.0_144

As a test I have done a copy and paste 'as is' from the reference implementation and run it with sysout statements to print the truncation and otp values for each counter.

The only changes made are: System.out and use of counter=movingFactor to print the movingFactor. None of which alter the logic. Note the differences in test data were found before adding the debug info.

Please see:
https://github.com/gerritjvv/cryptoplayground/tree/master/hmac/java/hmac/src/test/java/org/funsec/hmac

UnitTest method:
https://github.com/gerritjvv/cryptoplayground/blob/master/hmac/java/hmac/src/test/java/org/funsec/hmac/HTOPTest.java#L83

Reference Impl:
https://github.com/gerritjvv/cryptoplayground/blob/master/hmac/java/hmac/src/test/java/org/funsec/hmac/HOTPRef.java

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