0 bit encryption?

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0 bit encryption?

bthom73

Hi, this might sound like an odd question, but I'm trying to figure
out if there's a way to "use" openssl without actually encrypting
anything.

We have a group of users here who wish to send email through
Thunderbird to a SMTP server (sendmail) that requires SSL/TLS
authentication/encryption. The complaint is that it takes too long for
Thunderbird to encrypt large attachments when sending email.
Email content security isn't a major concern in our situation but we
do want to keep the SSL/TLS authentication in order to prevent
others outside the group from relaying through the SMTP server.
Sendmail depends on openssl for the SSL/TLS portion, so I'm
trying to figure out if there's a way we can modify the SMTP server
to not attempt or require encryption from the email clients while
leaving the basic structure (sendmail/openssl) in place. Maybe set
the encryption strength to zero bits or something similar? I'm not
too openssl savvy, so any details would be greatly appreciated.

Thanks for any info.

-Brian



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Re: 0 bit encryption?

Victor Duchovni
On Fri, Nov 17, 2006 at 08:14:26PM -0500, Brian Thompson wrote:

> Hi, this might sound like an odd question, but I'm trying to figure
> out if there's a way to "use" openssl without actually encrypting
> anything.
>
> We have a group of users here who wish to send email through
> Thunderbird to a SMTP server (sendmail) that requires SSL/TLS
> authentication/encryption. The complaint is that it takes too long for
> Thunderbird to encrypt large attachments when sending email.

This complaint is likely bogus, AES runs with ease (plenty of CPU left)
at over 100Mbp/s. Unless this is 1Gbps/s connection, there should be no
noticeable delay.

> Email content security isn't a major concern in our situation but we
> do want to keep the SSL/TLS authentication in order to prevent
> others outside the group from relaying through the SMTP server.
> Sendmail depends on openssl for the SSL/TLS portion, so I'm
> trying to figure out if there's a way we can modify the SMTP server
> to not attempt or require encryption from the email clients while
> leaving the basic structure (sendmail/openssl) in place. Maybe set
> the encryption strength to zero bits or something similar? I'm not
> too openssl savvy, so any details would be greatly appreciated.

This violates the purpose of the controls, if you don't want to mandate
an encrypted channel, change the Sendmail configuration to not require it.

--
        Viktor.
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Re: 0 bit encryption?

Marek.Marcola
In reply to this post by bthom73
Hello,
> Hi, this might sound like an odd question, but I'm trying to figure
> out if there's a way to "use" openssl without actually encrypting
> anything.
Of course, SSL/TLS consists of three purposes:
 - peer authentication (where, for example, RSA is used)
 - data encryption (DES, AES ...)
 - data integrity (SHA1, MD5)

> We have a group of users here who wish to send email through
> Thunderbird to a SMTP server (sendmail) that requires SSL/TLS
> authentication/encryption. The complaint is that it takes too long for
> Thunderbird to encrypt large attachments when sending email.
> Email content security isn't a major concern in our situation but we
> do want to keep the SSL/TLS authentication in order to prevent
> others outside the group from relaying through the SMTP server.
> Sendmail depends on openssl for the SSL/TLS portion, so I'm
> trying to figure out if there's a way we can modify the SMTP server
> to not attempt or require encryption from the email clients while
> leaving the basic structure (sendmail/openssl) in place. Maybe set
> the encryption strength to zero bits or something similar? I'm not
> too openssl savvy, so any details would be greatly appreciated.
If you want  to not encrypt your data, but you want to have
client authentication (with RSA key) you may use eNULL cipher:

$ openssl ciphers -v eNULL
NULL-SHA   SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
NULL-MD5   SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5

this means that if server wants to verify client authentication
than RSA key will be used, after proper authentication
data transfered between peers will be no encrypted (Enc=Null)
but data integrity will be checked/preserved (Mac=SHA1,MD5)
which means that modification of this data will by third party
will be detected and in such case SSL tunnel will be disconnected
(and peers notified).

In this situation, key_material will be generated but only
keys for data integrity (HMAC for TSL1 for example) will be used.

Best regards,
--
Marek Marcola <[hidden email]>

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Re: 0 bit encryption?

Girish Venkatachalam-2
In reply to this post by Victor Duchovni
On Fri, Nov 17, 2006 at 11:04:48PM -0500, Victor Duchovni wrote:
> On Fri, Nov 17, 2006 at 08:14:26PM -0500, Brian Thompson wrote:
> > We have a group of users here who wish to send email through
> > Thunderbird to a SMTP server (sendmail) that requires SSL/TLS
> > authentication/encryption. The complaint is that it takes too long for
> > Thunderbird to encrypt large attachments when sending email.
>
> This complaint is likely bogus, AES runs with ease (plenty of CPU left)
> at over 100Mbp/s. Unless this is 1Gbps/s connection, there should be no
> noticeable delay.

Agree. This is most definitely bogus and utter bullshit.

Symmetric crypto in particular AES is a breeze on modern desktop hardware.

Thunderbird may have other issues I am not aware of.

>
> > Email content security isn't a major concern in our situation but we
> > do want to keep the SSL/TLS authentication in order to prevent
> > others outside the group from relaying through the SMTP server.
> > Sendmail depends on openssl for the SSL/TLS portion, so I'm
> > trying to figure out if there's a way we can modify the SMTP server
> > to not attempt or require encryption from the email clients while
> > leaving the basic structure (sendmail/openssl) in place. Maybe set
> > the encryption strength to zero bits or something similar? I'm not
> > too openssl savvy, so any details would be greatly appreciated.
>
> This violates the purpose of the controls, if you don't want to mandate
> an encrypted channel, change the Sendmail configuration to not require it.

You don't stand to gain much by not encrypting and only authenticating.

There is no piecemeal security solution.

Best,
Girish
--
Linux is for folks who hate Windoze.

FreeBSD is for folks who love UNIX.

OpenBSD is for folks who can't live without UNIX.
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Re: 0 bit encryption?

Bear Giles

> You don't stand to gain much by not encrypting and only authenticating.
>  
Encryption and authentication are very different things. They're related
since encryption without authentication leaves you open to
man-in-the-middle attacks, but there are plenty of situations where you
just need authentication and message integrity.

Don't forget that message encryption may be locally illegal or
prohibited. Some countries outlaw encryption entirely, and large
organizations may require all email traverse internal VPNs in the clear.
In both cases correspondents may still want to have confidence that the
remote system is who it claims to be.

(Aside: why would an organization insist on internal cleartext? One big
cause is sexual and racial harassment complaints. Settlements routinely
require the organization to monitor all email for offensive content.)


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Re: Thunderbird delays..."was 0 bit encryption?"

bthom73
In reply to this post by Marek.Marcola


Marek Marcola wrote:

>Hello,
>  
>
>>Hi, this might sound like an odd question, but I'm trying to figure
>>out if there's a way to "use" openssl without actually encrypting
>>anything.
>>    
>>
>Of course, SSL/TLS consists of three purposes:
> - peer authentication (where, for example, RSA is used)
> - data encryption (DES, AES ...)
> - data integrity (SHA1, MD5)
>
>  
>
>>We have a group of users here who wish to send email through
>>Thunderbird to a SMTP server (sendmail) that requires SSL/TLS
>>authentication/encryption. The complaint is that it takes too long for
>>Thunderbird to encrypt large attachments when sending email.
>>Email content security isn't a major concern in our situation but we
>>do want to keep the SSL/TLS authentication in order to prevent
>>others outside the group from relaying through the SMTP server.
>>Sendmail depends on openssl for the SSL/TLS portion, so I'm
>>trying to figure out if there's a way we can modify the SMTP server
>>to not attempt or require encryption from the email clients while
>>leaving the basic structure (sendmail/openssl) in place. Maybe set
>>the encryption strength to zero bits or something similar? I'm not
>>too openssl savvy, so any details would be greatly appreciated.
>>    
>>
>If you want  to not encrypt your data, but you want to have
>client authentication (with RSA key) you may use eNULL cipher:
>
>$ openssl ciphers -v eNULL
>NULL-SHA   SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
>NULL-MD5   SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
>
>this means that if server wants to verify client authentication
>than RSA key will be used, after proper authentication
>data transfered between peers will be no encrypted (Enc=Null)
>but data integrity will be checked/preserved (Mac=SHA1,MD5)
>which means that modification of this data will by third party
>will be detected and in such case SSL tunnel will be disconnected
>(and peers notified).
>
>In this situation, key_material will be generated but only
>keys for data integrity (HMAC for TSL1 for example) will be used.
>
>Best regards,
>  
>
Thanks for the info Marek, much appreciated. I used the above info
and it worked for reducing the key strength, but it didn't solve the delays
in sending email. Still good to know though since it's one less thing to
consider. Must be something else that's causing the long delays. Even
for short emails such as this, it takes an extra 45 seconds or so compared
to sending the email with SSL/TLS completely disabled. Maybe it's the
certificate verification step that's causing the Thunderbird delays. The
CA and the certificate we're using on the server side are self-generated
by openssl.

-Brian
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Re: 0 bit encryption?

Victor Duchovni
In reply to this post by Bear Giles
On Sat, Nov 18, 2006 at 08:17:13AM -0700, Bear Giles wrote:

> (Aside: why would an organization insist on internal cleartext? One big
> cause is sexual and racial harassment complaints. Settlements routinely
> require the organization to monitor all email for offensive content.)

This applies to encrypting email content (S/MIME, PGP, ...), but not to
use of TLS, which only leaves the delivered email in the clear.

--
        Viktor.
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Re: 0 bit encryption?

bthom73


Victor Duchovni wrote:

>On Sat, Nov 18, 2006 at 08:17:13AM -0700, Bear Giles wrote:
>
>  
>
>>(Aside: why would an organization insist on internal cleartext? One big
>>cause is sexual and racial harassment complaints. Settlements routinely
>>require the organization to monitor all email for offensive content.)
>>    
>>
>
>This applies to encrypting email content (S/MIME, PGP, ...), but not to
>use of TLS, which only leaves the delivered email in the clear.
>
>  
>

According to the sendmail docs:
"privacy/confidentiality: the transmission of an e-mail between a client
and server utilizing STARTTLS can not be read and retranslated into
plaintext provided a sufficiently secure ciphersuite has been negotiated."

Reference:
http://www.sendmail.org/~ca/email/starttls.html

-Brian

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Re: 0 bit encryption?

Victor Duchovni
On Sat, Nov 18, 2006 at 11:13:45AM -0500, Brian Thompson wrote:

> >This applies to encrypting email content (S/MIME, PGP, ...), but not to
> >use of TLS, which leaves the delivered email in the clear.
>
> According to the sendmail docs:
> "privacy/confidentiality: the transmission of an e-mail between a client
> and server utilizing STARTTLS can not be read and retranslated into
> plaintext provided a sufficiently secure ciphersuite has been negotiated."
>

This is silly. Note the word *transmission*. Email supervision does not
require clear-text transmission, because it is done against stored data,
not eavesdropped network packets. Over and out.

--
        Viktor.
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Re: Thunderbird delays..."was 0 bit encryption?"

Marek.Marcola
In reply to this post by bthom73
Hello,
> Thanks for the info Marek, much appreciated. I used the above info
> and it worked for reducing the key strength, but it didn't solve the delays
> in sending email. Still good to know though since it's one less thing to
> consider. Must be something else that's causing the long delays. Even
> for short emails such as this, it takes an extra 45 seconds or so compared
> to sending the email with SSL/TLS completely disabled. Maybe it's the
> certificate verification step that's causing the Thunderbird delays. The
> CA and the certificate we're using on the server side are self-generated
> by openssl.
My suggestion is to double check DNS resolving system.
Such long delays when connecting may be caused be
problems with reverse DNS.
On Linux you may check this with:

$ dig some.domain.name
$ dig -x some.ip.number

If (for examle) sendmail checks some fields in certificate
(CN) and tries resolve this to IP address and next to domain
name (DNS double check) then this may generate such delays.

Best regards,
--
Marek Marcola <[hidden email]>

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Re: 0 bit encryption?

Bear Giles
In reply to this post by Victor Duchovni
Victor Duchovni wrote:

> On Sat, Nov 18, 2006 at 11:13:45AM -0500, Brian Thompson wrote:
>
>  
>>> This applies to encrypting email content (S/MIME, PGP, ...), but not to
>>> use of TLS, which leaves the delivered email in the clear.
>>>      
>> According to the sendmail docs:
>> "privacy/confidentiality: the transmission of an e-mail between a client
>> and server utilizing STARTTLS can not be read and retranslated into
>> plaintext provided a sufficiently secure ciphersuite has been negotiated."
>>
>>    
>
> This is silly. Note the word *transmission*. Email supervision does not
> require clear-text transmission, because it is done against stored data,
> not eavesdropped network packets. Over and out.
Hardly. You're trying to treat potentially legal problems as purely
technical ones. Organizations hauled into court can't always say "trust
me", and organizations may want to quietly use outside consultants if
they're investigating/monitoring their own IT departments.

Then there's the whole "cryptography is illegal in the People's Republic
of Freedonia" factor....
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Re: Thunderbird delays..."was 0 bit encryption?"

Alan Buxey
In reply to this post by Marek.Marcola
Hi,

> My suggestion is to double check DNS resolving system.
> Such long delays when connecting may be caused be
> problems with reverse DNS.
> On Linux you may check this with:
>
> $ dig some.domain.name
> $ dig -x some.ip.number
>
> If (for examle) sendmail checks some fields in certificate
> (CN) and tries resolve this to IP address and next to domain
> name (DNS double check) then this may generate such delays.

identd may also cause large delays . once again, not an OpenSSL issue

alan
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