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I've created an encrypted backup in 2004, using losetup -e. I still know the passphrase, so I should be fine, but losetup is gone in the linux distributions I use.

I still have a bash script for decryption, basically it reads

SEED="JMnvk8bp2y3P"
losetup -e aes128 -S "$SEED" -H sha256 "$LOOP" "$DATA"
mount -t ext2 "$LOOP" "$MOUNTPOINT"

While cryptsetup is supposedly backwards-compatible, it doesn't support a cryptographic seed (losetup's -S).

Probably using an old bootable-CD linux distribution would help, but how do I find one that supports losetup -e? I can't download some five GB just to find out.

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    try sysresccd 2.4.1 - 3.0.0 (you can download old versions from their site) – frostschutz Nov 23 '15 at 13:29
  • Are you sure that wasn't a local or distribution-specific patch? None of the versions in Debian have ever mentioned -S in their man page or in their --help output. – Gilles Nov 23 '15 at 23:27
  • An old bootable CD should only be around 650 MB, Mint & ubuntu live iso's are only 1 to 1.5GB, not 5GB – Xen2050 Nov 24 '15 at 5:59
  • @Gilles, (I'm pretty sure I used some version of Debian to create it in the first place.) How did you search historical manpages? – bayer Nov 25 '15 at 22:39
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    @bayer I have a chroot with every version of Debian since slink. zgrep -l -e -e /BIG/chroot/*/usr/{share/,}man/man8/losetup.8.gz lists them all, but zgrep -l -e -S /BIG/chroot/*/usr/{share/,}man/man8/losetup.8.gz finds nothing. Nor does zgrep seed /BIG/chroot/*/usr/{share/,}man/man8/losetup.8.gz – Gilles Nov 25 '15 at 22:43
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I was able to get my losetup -e-style image file mounted with cryptsetup.

Formerly, I used

    losetup -e twofish /dev/loop0 disk-image-file.img
    mount -t ext3 /dev/loop0 /mnt/mount-point

I have replaced this with:

    cryptsetup -c twofish --type plain open disk-image-file.img the-disk
    mount -t ext3 /dev/mapper/the-disk /mnt/mount-point
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Following @frostschutz 's suggestion, I downloaded SystemRescueCd-x86-2.8.1 which includes a version of losetup that provides the -S seed argument. Thank y'all!

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