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From "Emmanuel Lecharny (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DIRKRB-27) [kerberos]org.apache.directory.server.kerberos.shared.crypto.encryption.DesCbcCrcEncryption shall not use java.util.zip.CRC32 to generate CRC32 checksum
Date Thu, 16 Sep 2010 22:33:34 GMT

    [ https://issues.apache.org/jira/browse/DIRKRB-27?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12910365#action_12910365
] 

Emmanuel Lecharny commented on DIRKRB-27:
-----------------------------------------

I'm wondering if the Java CRC32 class can be used in this case ?

http://download.oracle.com/javase/6/docs/api/java/util/zip/CRC32.html

> [kerberos]org.apache.directory.server.kerberos.shared.crypto.encryption.DesCbcCrcEncryption
shall not use java.util.zip.CRC32 to generate CRC32 checksum
> --------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DIRKRB-27
>                 URL: https://issues.apache.org/jira/browse/DIRKRB-27
>             Project: Directory Kerberos
>          Issue Type: Bug
>    Affects Versions: 2.0.0
>            Reporter: Leo Li
>            Assignee: Emmanuel Lecharny
>             Fix For: 2.0.0
>
>         Attachments: Crc32Checksum.patch
>
>
> As in RFC3961 [Page 17]: 
> 6.1.3.  CRC-32 Checksum
> This CRC-32 checksum calculates a checksum based on a cyclic
>    redundancy check as described in ISO 3309 [CRC] but modified as
>    described below.  
> ...
> The CRC-32 checksum used in the des-cbc-crc encryption mode is
>    identical to the 32-bit FCS described in ISO 3309 with two
>    exceptions: The sum with the all-ones polynomial times x**k is
>    omitted, and the final remainder is not ones-complemented.  ISO 3309
>    describes the FCS in terms of bits, whereas this document describes
>    the Kerberos protocol in terms of octets.  To clarify the ISO 3309
>    definition for the purpose of computing the CRC-32 in the des-cbc-crc
>    encryption mode, the ordering of bits in each octet shall be assumed
>    to be LSB first.  Given this assumed ordering of bits within an
>    octet, the mapping of bits to polynomial coefficients shall be
>    identical to that specified in ISO 3309.
> And RFC 3961 also gives test data in its Appendix A.5:
> RFC 3961         Encryption and Checksum Specifications    February 2005
>    internally for such a number is irrelevant; the octet sequence
>    generated is what is important.)
>    mod-crc-32("foo") =                                     33 bc 32 73
>    mod-crc-32("test0123456789") =                          d6 88 3e b8
>    mod-crc-32("MASSACHVSETTS INSTITVTE OF TECHNOLOGY") =   f7 80 41 e3
>    mod-crc-32(8000) =                                      4b 98 83 3b
>    mod-crc-32(0008) =                                      32 88 db 0e
>    mod-crc-32(0080) =                                      20 83 b8 ed
>    mod-crc-32(80) =                                        20 83 b8 ed
>    mod-crc-32(80000000) =                                  3b b6 59 ed
>    mod-crc-32(00000001) =                                  96 30 07 77

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