REXX, SPF, Internet drafts


MD5 test suite version 1.8

The MD5 test suite 1.8 finally mentions RFC 6151, fixes a minor exit code bug in version 1.7, supports the web-safe base64 encoding specified in RFC 4648 as base64url alphabet, uses the USCYBERCOM easter egg as MD5 streaming test case, and covers the collision announced by Tao Xie and Dengguo Feng in December 2010 (2 of 512 bits modified). Read their PDF (one page) for details of the offered bounty for anybody who finds another collision of this type.



Some of my web pages are still messy and on their way to a new hoster, but there is a new version of checkmbr.rex (REXX script) maybe interesting for users of TestDisk. The script can analyze MBR disks on Windows platforms using \\.\PHYSICALDRIVEn for n=0..9, and identifies unused sectors caused by generous partitioning or by FAT and NTFS sizes not exactly fitting into their given partition. While at it the script creates base 64 backups of various boot sectors. Fixed bugs and new features:

  • The max. cluster numbers for FAT12/16/32 were "off by one". The hardwired limits are now 4084, 65524, and 268435444.
  • Added partition type 27h "WinRE" for a hidden windows recovery partition and file system NTFS.
  • exFAT uses partition type 07h also used by NTFS. This is unsupported and should result in lots of "NTFS errors" for exFAT (untested).
  • UEFI disks start with a protective MBR (partition type EEh). This is now reported, but checkMBR analyzes only MBR disks.
  • VFD (virtual floppy disk) and fixed VHD (virtual hard disk) files can now be given instead of a physical drive number.

The new VHD feature would fail for ooREXX 3.x and VHDs greater than 2 GB, get ooREXX 4.x. Many identified partition types are untested or ambiguous, e.g., I've never seen an EFI FAT type EFh roughly corresponding to a Windows system NTFS partition on MBR disks, or the partition types allegedly used by the FreeDOS FDISK tool to hide FAT, NTFS, or extended partitions.


about: ftp:

There are I-Ds for two URI schemes:

  1. about: URIs tackle about:blank and similar beasts.
  2. ftp: URIs are another missing piece in the quest to finally get rid of RFC 1738.

Please review these drafts and send any feedback to the relevant IETF mailing lists — subscriptions are cheap, they cost you a working e-mail address. ;-)

So far nobody volunteered to finish the existing file: URI I-D (2005).  There are some dragons with respect to different browsers and operating systems, notably IE vs. Firefox and Windows vs. Linux, but really, almost any file: URI scheme RFC based on the work for other schemes would be better than RFC 1738 vintage 1994 today.  And you are not forced to emulate some negative records created by me for RFC 5538.  I think file: and ftp: URIs are the last missing pieces in this puzzle.  Check out the mailserver: (RFC 6196) and tn3270: (RFC 6270) URI schemes for pieces added in 2011.

Completely unrelated, and not deserving a separate article:  I've recently added a CC-BY-SA license for this blog.  That is mostly an experiment to show my support for Creative Commons and Wikimedia Commons as explained on my commons page with a fascinating (but long) video of a CCC lecture by Lawrence Lessig in 2006.  Clearly I can't revert this license to some more restrictive form for existing pages, but maybe I'll change it to public domain in the future if I feel like it, or if somebody asks for it with a sound reason (from my POV).


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