# block cipher mode



## bes (Aug 7, 2010)

What GELI uses : CBC or CBC-ESSIV ?


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## DutchDaemon (Aug 7, 2010)

CBC-ESSIV, according to http://mareichelt.de/pub/notmine/linuxbsd-comparison.html


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## bes (Aug 7, 2010)

Thanks,it's good.
But why dmesg |grep ELI said:

```
GEOM_ELI: Device da1s1a.eli created.
GEOM_ELI: Encryption: AES-CBC 256
GEOM_ELI:     Crypto: software
```
?


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## bes (Sep 29, 2010)

answer from Pawel Jakub Dawidek:


> GELI uses CBC with unpredictable IV. IV is generated by calculating
> SHA256 from IV-Key (which is secret) and sector offset. Not sure if this
> fully matches ESSIV definition.



DutchDaemon,
Do you know who is maintaining this page:http://mareichelt.de/pub/notmine/linuxbsd-comparison.html?


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## DutchDaemon (Sep 29, 2010)

No idea. Try mailing something like postmaster@, webmaster@, admin@ that domain.


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## bes (Oct 19, 2010)

Good news,
Recent GELI additions.

According to new man GELI(8) FreeBSD-9:



> geli supports two encryption modes: XTS, which was standarized as IEE
> P1619 and CBC with unpredictable IV.  The CBC mode used by geli is very
> similar to the mode ESSIV.



Solved.


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