[RFC] Ceph encryption support

[RFC] Ceph encryption support

[Li Wang]

Hi,
   We want to implement encryption support for Ceph.
   Currently, we have the draft design,

1 When user mount a ceph directory for the first time, he can specify a 
passphrase and the encryption algorithm and length of key etc. These 
will be stored as extend attribute of the current root directory, of 
course, with the passphrase being hashed several times, call it TOKEN.
2 When user try to mount an encrypted directory, a passphrase is 
required to given, then hash and compare with the stored TOKEN, if 
equal, accept to mount, otherwise reject to mount.
3 When a file is created, a random key (FEK, file encryption key) is 
generated, and this key is encrypted by TOKEN, we get EFEK (encrypted 
FEK), the EFEK and other encryption related information inherited from 
the root directory are stored in the extend attribute of file.
4 When a file is opened, retrieve the extend attribute, we get EFEK,
use TOKEN to decrypt EFEK, get FEK, buffered in the inode
5 When a file is read in readpage()/readpages(), the encrypted pages are 
decrypted transparently by using FEK, and the plain data are sent to 
application
6 When a file is written in writepage()/writepages(), the pages are 
encrypted transparently by using FEK, and then written to OSDs.

Some points,
1 We do client side encryption, the advantages are,
   (1) The data over network are encrypted;
   (2) OSDs are intended to do io intensive job, we donot wanna bother 
them to do cpu intensive job, thus we can use cheap and low power machines
   (3) The implementation is OSD transparent, and mostly MDS 
transparent, enjoys the simplification.
2 What about if no page cache?
   Block cipher algorithm is more secure than stream cipher algorithm, 
so we prefer the former. If no page cache, we have two choices, with 
encryption enabled, the same file is not allowed by opened by the second 
writer, alternatively, we enforce O_LAZYIO on the file, but application 
is supposed to be aware of this.

We plan to submit it as a blueprint for the incoming CDS, comments are 
welcome.

Cheers,
Li Wang

Re: [RFC] Ceph encryption support

[Gregory Farnum]

On Tue, Nov 12, 2013 at 6:10 AM, Li Wang <liwang@ubuntukylin.com> wrote:
> Hi,
>   We want to implement encryption support for Ceph.
>   Currently, we have the draft design,
>
> 1 When user mount a ceph directory for the first time, he can specify a
> passphrase and the encryption algorithm and length of key etc. These will be
> stored as extend attribute of the current root directory, of course, with
> the passphrase being hashed several times, call it TOKEN.
> 2 When user try to mount an encrypted directory, a passphrase is required to
> given, then hash and compare with the stored TOKEN, if equal, accept to
> mount, otherwise reject to mount.

How would this work? If I mount the root directory and then try to
navigate down into an encrypted directory, when do I get asked for the
passphrase?

> 3 When a file is created, a random key (FEK, file encryption key) is
> generated, and this key is encrypted by TOKEN, we get EFEK (encrypted FEK),
> the EFEK and other encryption related information inherited from the root
> directory are stored in the extend attribute of file.

So the hash is visible to clients who don't support encryption? Or do
you want to hide it somehow?

> 4 When a file is opened, retrieve the extend attribute, we get EFEK,
> use TOKEN to decrypt EFEK, get FEK, buffered in the inode
> 5 When a file is read in readpage()/readpages(), the encrypted pages are
> decrypted transparently by using FEK, and the plain data are sent to
> application
> 6 When a file is written in writepage()/writepages(), the pages are
> encrypted transparently by using FEK, and then written to OSDs.
>
> Some points,
> 1 We do client side encryption, the advantages are,
>   (1) The data over network are encrypted;
>   (2) OSDs are intended to do io intensive job, we donot wanna bother them
> to do cpu intensive job, thus we can use cheap and low power machines
>   (3) The implementation is OSD transparent, and mostly MDS transparent,
> enjoys the simplification.
> 2 What about if no page cache?
>   Block cipher algorithm is more secure than stream cipher algorithm, so we
> prefer the former. If no page cache, we have two choices, with encryption
> enabled, the same file is not allowed by opened by the second writer,
> alternatively, we enforce O_LAZYIO on the file, but application is supposed
> to be aware of this.
>
> We plan to submit it as a blueprint for the incoming CDS, comments are
> welcome.

This doesn't sound infeasible, but I'll welcome the details in a
blueprint. :) The main thing I'm worried about is that if anybody
breaks the TOKEN they have access to everything, and the hash is going
to be available to anybody who wants to see it.
When I've thought about this in the past I've tended more towards a
system that uses time-based passcodes derived from a secret which the
MDS and OSD share, which lets you do sharing without giving the client
unlimited permissions on a file. But that requires a lot more
modifications, and your system has some nice properties as well. You
might also find
https://www.usenix.org/system/files/conference/fast13/fast13-final142.pdf
interesting — it's a very different approach, but people have done
some thinking about distributed filesystem security before and it's
always good to consider what's out there before starting. :)
-Greg
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Re: [RFC] Ceph encryption support

[Li Wang]

Hi Gregory,
   Thanks for your comments.

On 11/13/2013 01:58 AM, Gregory Farnum wrote:
> On Tue, Nov 12, 2013 at 6:10 AM, Li Wang <liwang@ubuntukylin.com> wrote:
>> Hi,
>>    We want to implement encryption support for Ceph.
>>    Currently, we have the draft design,
>>
>> 1 When user mount a ceph directory for the first time, he can specify a
>> passphrase and the encryption algorithm and length of key etc. These will be
>> stored as extend attribute of the current root directory, of course, with
>> the passphrase being hashed several times, call it TOKEN.
>> 2 When user try to mount an encrypted directory, a passphrase is required to
>> given, then hash and compare with the stored TOKEN, if equal, accept to
>> mount, otherwise reject to mount.
>
> How would this work? If I mount the root directory and then try to
> navigate down into an encrypted directory, when do I get asked for the
> passphrase?
>

I think the duty of encryption is to protect the confidence of the 
content of files, that is, user cannot view the plain text if without 
valid password. But not to prevent user from navigating into the 
directory, even damage and delete the file, those are something should 
be done by access control (acl, selinux etc). So, our design for the 
initial version of encryption is that we donot care this, user could 
navigate into the encyrpted directory, so what, he will see all 
encrypted text, and the encrypted file name. This is also what eCryptfs 
is doing, user could read/write/delete the encrypted file directly from 
the lower file system, provided the access control allows him to do so.

>> 3 When a file is created, a random key (FEK, file encryption key) is
>> generated, and this key is encrypted by TOKEN, we get EFEK (encrypted FEK),
>> the EFEK and other encryption related information inherited from the root
>> directory are stored in the extend attribute of file.
>
> So the hash is visible to clients who don't support encryption? Or do
> you want to hide it somehow?
>

So we plan to not to store Token at all. If you enter wrong pass phrase, 
you could still mount the directory, but you will see encrypted text. 
This is basically what eCryptfs is doing. Maybe we could improve user 
experience a little bit by using HMAC on Token to get a hash value 
HToken to be stored. But HToken is only used to warn the valid user if 
he accidentally input wrong pass phrase.

So in a word, we think that encryption is for protecting the current 
content of files, rather than preventing damaging/deleting the files, 
that is what access control is supposed to do. And, in any case, we 
could hardly prevent the user using old client (without encryption 
support) or manipulating rados directly to damage/delete the encrypted 
file. But one thing we do could consider is to use HMAC to warn the 
valid user that the file has been modified by other unauthorized person.

>> 4 When a file is opened, retrieve the extend attribute, we get EFEK,
>> use TOKEN to decrypt EFEK, get FEK, buffered in the inode
>> 5 When a file is read in readpage()/readpages(), the encrypted pages are
>> decrypted transparently by using FEK, and the plain data are sent to
>> application
>> 6 When a file is written in writepage()/writepages(), the pages are
>> encrypted transparently by using FEK, and then written to OSDs.
>>
>> Some points,
>> 1 We do client side encryption, the advantages are,
>>    (1) The data over network are encrypted;
>>    (2) OSDs are intended to do io intensive job, we donot wanna bother them
>> to do cpu intensive job, thus we can use cheap and low power machines
>>    (3) The implementation is OSD transparent, and mostly MDS transparent,
>> enjoys the simplification.
>> 2 What about if no page cache?
>>    Block cipher algorithm is more secure than stream cipher algorithm, so we
>> prefer the former. If no page cache, we have two choices, with encryption
>> enabled, the same file is not allowed by opened by the second writer,
>> alternatively, we enforce O_LAZYIO on the file, but application is supposed
>> to be aware of this.
>>
>> We plan to submit it as a blueprint for the incoming CDS, comments are
>> welcome.
>
> This doesn't sound infeasible, but I'll welcome the details in a
> blueprint. :) The main thing I'm worried about is that if anybody
> breaks the TOKEN they have access to everything, and the hash is going
> to be available to anybody who wants to see it.
> When I've thought about this in the past I've tended more towards a
> system that uses time-based passcodes derived from a secret which the
> MDS and OSD share, which lets you do sharing without giving the client
> unlimited permissions on a file. But that requires a lot more
> modifications, and your system has some nice properties as well. You
> might also find
> https://www.usenix.org/system/files/conference/fast13/fast13-final142.pdf
> interesting — it's a very different approach, but people have done
> some thinking about distributed filesystem security before and it's
> always good to consider what's out there before starting. :)
> -Greg
>
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Re: [RFC] Ceph encryption support

[Alex Elsayed]

Li Wang wrote:

> Hi,
>    We want to implement encryption support for Ceph.
>    Currently, we have the draft design,
> 
> 1 When user mount a ceph directory for the first time, he can specify a
> passphrase and the encryption algorithm and length of key etc. These
> will be stored as extend attribute of the current root directory, of
> course, with the passphrase being hashed several times, call it TOKEN.
> 2 When user try to mount an encrypted directory, a passphrase is
> required to given, then hash and compare with the stored TOKEN, if
> equal, accept to mount, otherwise reject to mount.
> 3 When a file is created, a random key (FEK, file encryption key) is
> generated, and this key is encrypted by TOKEN, we get EFEK (encrypted
> FEK), the EFEK and other encryption related information inherited from
> the root directory are stored in the extend attribute of file.
> 4 When a file is opened, retrieve the extend attribute, we get EFEK,
> use TOKEN to decrypt EFEK, get FEK, buffered in the inode
> 5 When a file is read in readpage()/readpages(), the encrypted pages are
> decrypted transparently by using FEK, and the plain data are sent to
> application
> 6 When a file is written in writepage()/writepages(), the pages are
> encrypted transparently by using FEK, and then written to OSDs.

Okay, this is sounding quite similar to eCryptfs so far. What that makes me 
wonder is whether eCryptfs can be used, as it's a _stacked_ filesystem.

> Some points,
> 1 We do client side encryption, the advantages are,
>    (1) The data over network are encrypted;
>    (2) OSDs are intended to do io intensive job, we donot wanna bother
> them to do cpu intensive job, thus we can use cheap and low power machines
>    (3) The implementation is OSD transparent, and mostly MDS
> transparent, enjoys the simplification.

This, however, is potentially problematic. At-rest encryption of files and 
encryption of moving data on the wire are different problems, and using one 
to try and address the other can lead to significant issues - in particular, 
this is why it is STRONGLY recommended not to rely on dm-crypt for security 
on network block devices like iSCSI without encrypting the transport using 
ipsec or similar.

> 2 What about if no page cache?
>    Block cipher algorithm is more secure than stream cipher algorithm,
> so we prefer the former. If no page cache, we have two choices, with
> encryption enabled, the same file is not allowed by opened by the second
> writer, alternatively, we enforce O_LAZYIO on the file, but application
> is supposed to be aware of this.

"Block cipher algorithm is more secure than stream cipher algorithm" cannot 
be taken as axiomatic. It being stated as such is something I find 
worrisome.

In particular, using AES in CTR mode (in which case it is essentially a 
random-access stream cipher) is in a number circumstances considerably more 
secure than AES in CBC mode. The stream ciphers Salsa20 and ChaCha are 
believed to be strong as well. Weaknesses in RC4 aren't due to being a 
stream cipher, but rather due to improper use (as in WEP, where the IVs were 
handled improperly) or flaws in the specific cipher.

How are you intending to handle integrity? Do you intend to use a MAC (and 
if so, PLEASE review the literature on mac-and-encrypt vs. mac-then-encrypt 
vs. encrypt-then-mac), or do you plan on using an AEAD cipher mode such as 
GCM (like eCryptfs does)? If your cipher mode uses IVs, how do you intend to 
generate them?

All of these have SIGNIFICANT security impact, and could lead to problems if 
left unaddressed or addressed improperly.

> We plan to submit it as a blueprint for the incoming CDS, comments are
> welcome.
> 
> Cheers,
> Li Wang

Re: [RFC] Ceph encryption support

[Li Wang]

Hi Alex,
   Thanks for your comments.


On 11/13/2013 09:07 AM, Alex Elsayed wrote:
> Li Wang wrote:
>
>> Hi,
>>     We want to implement encryption support for Ceph.
>>     Currently, we have the draft design,
>>
>> 1 When user mount a ceph directory for the first time, he can specify a
>> passphrase and the encryption algorithm and length of key etc. These
>> will be stored as extend attribute of the current root directory, of
>> course, with the passphrase being hashed several times, call it TOKEN.
>> 2 When user try to mount an encrypted directory, a passphrase is
>> required to given, then hash and compare with the stored TOKEN, if
>> equal, accept to mount, otherwise reject to mount.
>> 3 When a file is created, a random key (FEK, file encryption key) is
>> generated, and this key is encrypted by TOKEN, we get EFEK (encrypted
>> FEK), the EFEK and other encryption related information inherited from
>> the root directory are stored in the extend attribute of file.
>> 4 When a file is opened, retrieve the extend attribute, we get EFEK,
>> use TOKEN to decrypt EFEK, get FEK, buffered in the inode
>> 5 When a file is read in readpage()/readpages(), the encrypted pages are
>> decrypted transparently by using FEK, and the plain data are sent to
>> application
>> 6 When a file is written in writepage()/writepages(), the pages are
>> encrypted transparently by using FEK, and then written to OSDs.
>
> Okay, this is sounding quite similar to eCryptfs so far. What that makes me
> wonder is whether eCryptfs can be used, as it's a _stacked_ filesystem.
>

eCryptfs has many limitations, mainly due to the stacked filesystem 
design. Linux VFS has no special support for stacked filesystem. The 
lower file system is never aware of the existence of upper file system, 
namely, eCryptfs. That will cause many problems from synchronization and 
consistency, especially for network and distributed file system. That is 
why eCryptfs can not work well on nfs, cifs, gfs etc. Basically, the 
problem is that even lower file system has done the synchronization, it 
will not notify eCryptfs. This also happens when you manipulate directly 
on the lower filesystem. For Ceph, it has already automatically 
synchronized the metadata while multiple clients operate the same file, 
using eCryptfs, the application could not see the synchronization, since 
eCryptfs has its own metadata cache, which is not synchronized. The 
second is that eCryptfs maintains its own page cache, which typically 
results in double-caching, consume much more memory.

>> Some points,
>> 1 We do client side encryption, the advantages are,
>>     (1) The data over network are encrypted;
>>     (2) OSDs are intended to do io intensive job, we donot wanna bother
>> them to do cpu intensive job, thus we can use cheap and low power machines
>>     (3) The implementation is OSD transparent, and mostly MDS
>> transparent, enjoys the simplification.
>
> This, however, is potentially problematic. At-rest encryption of files and
> encryption of moving data on the wire are different problems, and using one
> to try and address the other can lead to significant issues - in particular,
> this is why it is STRONGLY recommended not to rely on dm-crypt for security
> on network block devices like iSCSI without encrypting the transport using
> ipsec or similar.
>

Ok. To guarantee the data confidence during networking transportation, 
it could set up the ipsec etc, that is not contradict with our plan, 
just need two times of encryption.

>> 2 What about if no page cache?
>>     Block cipher algorithm is more secure than stream cipher algorithm,
>> so we prefer the former. If no page cache, we have two choices, with
>> encryption enabled, the same file is not allowed by opened by the second
>> writer, alternatively, we enforce O_LAZYIO on the file, but application
>> is supposed to be aware of this.
>
> "Block cipher algorithm is more secure than stream cipher algorithm" cannot
> be taken as axiomatic. It being stated as such is something I find
> worrisome.
>
> In particular, using AES in CTR mode (in which case it is essentially a
> random-access stream cipher) is in a number circumstances considerably more
> secure than AES in CBC mode. The stream ciphers Salsa20 and ChaCha are
> believed to be strong as well. Weaknesses in RC4 aren't due to being a
> stream cipher, but rather due to improper use (as in WEP, where the IVs were
> handled improperly) or flaws in the specific cipher.
>

No problem, we do not quite care which cipher to use, as long as kernel 
crypto API support, we can leave it the user's choice as eCryptfs does.

> How are you intending to handle integrity? Do you intend to use a MAC (and
> if so, PLEASE review the literature on mac-and-encrypt vs. mac-then-encrypt
> vs. encrypt-then-mac), or do you plan on using an AEAD cipher mode such as
> GCM (like eCryptfs does)? If your cipher mode uses IVs, how do you intend to
> generate them?
>
> All of these have SIGNIFICANT security impact, and could lead to problems if
> left unaddressed or addressed improperly.
>

Do we really need integrity, I think that is mainly used to detect the 
unauthorized modification to the encrypted text. If need, we can 
consider to use HMAC or GCM.

>> We plan to submit it as a blueprint for the incoming CDS, comments are
>> welcome.
>>
>> Cheers,
>> Li Wang
>
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: [RFC] Ceph encryption support

[Alex Elsayed]

Li Wang wrote:

> Hi Alex,
>    Thanks for your comments.
> 
> 
> On 11/13/2013 09:07 AM, Alex Elsayed wrote:
>> Li Wang wrote:
>>
>>> Hi,
>>>     We want to implement encryption support for Ceph.
>>>     Currently, we have the draft design,
>>>
>>> 1 When user mount a ceph directory for the first time, he can specify a
>>> passphrase and the encryption algorithm and length of key etc. These
>>> will be stored as extend attribute of the current root directory, of
>>> course, with the passphrase being hashed several times, call it TOKEN.
>>> 2 When user try to mount an encrypted directory, a passphrase is
>>> required to given, then hash and compare with the stored TOKEN, if
>>> equal, accept to mount, otherwise reject to mount.
>>> 3 When a file is created, a random key (FEK, file encryption key) is
>>> generated, and this key is encrypted by TOKEN, we get EFEK (encrypted
>>> FEK), the EFEK and other encryption related information inherited from
>>> the root directory are stored in the extend attribute of file.
>>> 4 When a file is opened, retrieve the extend attribute, we get EFEK,
>>> use TOKEN to decrypt EFEK, get FEK, buffered in the inode
>>> 5 When a file is read in readpage()/readpages(), the encrypted pages are
>>> decrypted transparently by using FEK, and the plain data are sent to
>>> application
>>> 6 When a file is written in writepage()/writepages(), the pages are
>>> encrypted transparently by using FEK, and then written to OSDs.
>>
>> Okay, this is sounding quite similar to eCryptfs so far. What that makes
>> me wonder is whether eCryptfs can be used, as it's a _stacked_
>> filesystem.
>>
> 
> eCryptfs has many limitations, mainly due to the stacked filesystem
> design. Linux VFS has no special support for stacked filesystem. The
> lower file system is never aware of the existence of upper file system,
> namely, eCryptfs. That will cause many problems from synchronization and
> consistency, especially for network and distributed file system. That is
> why eCryptfs can not work well on nfs, cifs, gfs etc. Basically, the
> problem is that even lower file system has done the synchronization, it
> will not notify eCryptfs. This also happens when you manipulate directly
> on the lower filesystem. For Ceph, it has already automatically
> synchronized the metadata while multiple clients operate the same file,
> using eCryptfs, the application could not see the synchronization, since
> eCryptfs has its own metadata cache, which is not synchronized. The
> second is that eCryptfs maintains its own page cache, which typically
> results in double-caching, consume much more memory.

Okay, all of that makes sense. I do think that looking _very_ closely at how 
ecryptfs works would be beneficial. For instance, it pads files prior to 
encryption to obscure the actual size and boundaries of the file (which 
mitigates known-plaintext attacks), it encrypts the names of files (which 
forces an attacker who wishes to perform an offline attack to expend more 
effort), etc.

>>> Some points,
>>> 1 We do client side encryption, the advantages are,
>>>     (1) The data over network are encrypted;
>>>     (2) OSDs are intended to do io intensive job, we donot wanna bother
>>> them to do cpu intensive job, thus we can use cheap and low power
>>> machines
>>>     (3) The implementation is OSD transparent, and mostly MDS
>>> transparent, enjoys the simplification.
>>
>> This, however, is potentially problematic. At-rest encryption of files
>> and encryption of moving data on the wire are different problems, and
>> using one to try and address the other can lead to significant issues -
>> in particular, this is why it is STRONGLY recommended not to rely on
>> dm-crypt for security on network block devices like iSCSI without
>> encrypting the transport using ipsec or similar.
>>
> 
> Ok. To guarantee the data confidence during networking transportation,
> it could set up the ipsec etc, that is not contradict with our plan,
> just need two times of encryption.

The issue here is that while iSCSI (which was my example above) is point-to-
point, and considerably easier to set up an encrypted tunnel for. With Ceph, 
the set of OSDs is expected to be large and variable. Opportunistic IPSEC 
has never really worked reliably (or been broadly deployed), and the other 
options aren't any better. It may be okay to say 'this is out of scope right 
now', but I want to ensure it's at least a running consideration.

>>> 2 What about if no page cache?
>>>     Block cipher algorithm is more secure than stream cipher algorithm,
>>> so we prefer the former. If no page cache, we have two choices, with
>>> encryption enabled, the same file is not allowed by opened by the second
>>> writer, alternatively, we enforce O_LAZYIO on the file, but application
>>> is supposed to be aware of this.
>>
>> "Block cipher algorithm is more secure than stream cipher algorithm"
>> cannot be taken as axiomatic. It being stated as such is something I find
>> worrisome.
>>
>> In particular, using AES in CTR mode (in which case it is essentially a
>> random-access stream cipher) is in a number circumstances considerably
>> more secure than AES in CBC mode. The stream ciphers Salsa20 and ChaCha
>> are believed to be strong as well. Weaknesses in RC4 aren't due to being
>> a stream cipher, but rather due to improper use (as in WEP, where the IVs
>> were handled improperly) or flaws in the specific cipher.
>>
> 
> No problem, we do not quite care which cipher to use, as long as kernel
> crypto API support, we can leave it the user's choice as eCryptfs does.

My objection wasn't to choosing block ciphers - it was to the reasoning 
given. Block ciphers aren't automatically more secure than stream ciphers, 
and assuming so can lead in problematic directions.

That said, eCryptfs *does* use block ciphers exclusively (while allowing the 
user to choose _which_ block cipher is used), due to having decided that the 
mode of operation would _always_ be GCM. Because GCM is an AEAD 
(Authenticated Encryption with Associated Data) mode, it ensures both 
confidentiality and integrity while avoiding the pitfalls around what 
ordering to use between padding, MAC, and encryption.

>> How are you intending to handle integrity? Do you intend to use a MAC
>> (and if so, PLEASE review the literature on mac-and-encrypt vs.
>> mac-then-encrypt vs. encrypt-then-mac), or do you plan on using an AEAD
>> cipher mode such as GCM (like eCryptfs does)? If your cipher mode uses
>> IVs, how do you intend to generate them?
>>
>> All of these have SIGNIFICANT security impact, and could lead to problems
>> if left unaddressed or addressed improperly.
>>
> 
> Do we really need integrity, I think that is mainly used to detect the
> unauthorized modification to the encrypted text. If need, we can
> consider to use HMAC or GCM.

I'd suggest using AEAD modes exclusively, because with a separate MAC there 
are a number of pitfalls to be carefully avoided. In particular, if you 
authenticate, then pad, then encrypt there are a number of timing attacks 
that become available; if you authenticate, encrypt, and concatenate the two 
then there are other vulnerabilities, etc.

Currently, the only AEAD mode in the kernel is GCM. Unfortunately, GCM has 
some efficiency issues on systems that don't have accelerated multiplication 
in GF(2^x), but the other AEAD modes available either also have efficiency 
issues or are potentially subject to patent issues[1].

I *would* suggest permitting any AEAD mode (even though only GCM is 
currently available), to allow the mode to be changed if a more efficient 
mode is added or a weakness is found in GCM. That's one place where I 
disagree with eCryptfs' choices - GCM is specifically hardcoded as I 
understand it.

>>> We plan to submit it as a blueprint for the incoming CDS, comments are
>>> welcome.

Looking forward to seeing it!

[1] OCB is patented, but that's not the issue - Rogaway has issued a 
royalty-free license for open-source software. The issue is that Gligor, 
Donescu, and Jutla (who have created other efficient AEAD modes) have 
patents that may-or-may-not ALSO apply, and have offered no such license. 
See http://www.cs.ucdavis.edu/~rogaway/ocb/ocb-faq.htm#patent:phil