Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Andy Polyakov]

> A run on my laptop gave these results:
> 
> : ; ./util/shlib_wrap.sh apps/openssl speed siphash lhash
> type 16 bytes 64 bytes256 bytes   1024 bytes   8192 
> bytes  16384 bytes
> lhash   147387.67k   147940.82k   144937.73k   147177.81k   
> 147095.55k   147679.91k
> siphash 119939.99k   223694.38k   283383.30k   305372.84k   
> 311760.21k   312120.66k
> 
> So it seems that for short strings, OPENSSL_LH_strhash (*) wins some,
> while siphash wins big for larger strings.

This is just *one* data point. Most notably what about 32-bit systems?
Another factor is code size, or rather time it takes to bring it into
cache, as well as what does it invalidate. Conventional benchmarks don't
tell you that, but it's only sensible to consider code size in
comparison to "typical" input size.

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Salz, Rich]

> Understood.  Can you further clarify whether you would like to maintain the 
> existing 20-year-old hand-rolled hash function for that purpose or are open 
> to using a more modern hash (not necessarily SIPhash; there are also things 
> like the Jenkins hash to consider)?

Because it works, because nobody has looked at our touched that code, because 
there are no security concerns and it's unclear if the speed gain(s) make a 
difference.
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Benjamin Kaduk]

On 01/11/2017 08:43 AM, Richard Levitte wrote:
> A note: I have absolutely nothing against the addition of SIPhash in
> our collection of hash algos.  My scepticism was only in regards to
> using it as a string hasher for our hash tables indexes.
>

Understood.  Can you further clarify whether you would like to maintain
the existing 20-year-old hand-rolled hash function for that purpose or
are open to using a more modern hash (not necessarily SIPhash; there are
also things like the Jenkins hash to consider)?

-Ben
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Peter Waltenberg]

 It pretty much has to be true of any keyed hash if you think about it. If it didn't distribute the hashes differently each time it wouldn't be working, if it distributes the hashes differently, performance has to be key dependent. And with a hash size the same as the key, at least one of the possible combinations has to be the pathological case.I can't currently see any possible vector for a flooding attack, well O.K., I certainly can if you use SipHash with random keys :) and even that would be hard to exploit, but otherwise no. If it's significantly faster using it with a pre-tested fixed key is probably fine, but it gives up the security characteristic you were after. My suspicion is also that simply compressing the string with XOR will work at least as well.Peter-"openssl-dev" <openssl-dev-boun...@openssl.org> wrote: -To: openssl-dev@openssl.orgFrom: "J. J. Farrell" <jeremy.farr...@oracle.com>Sent by: "openssl-dev" <openssl-dev-boun...@openssl.org>Date: 01/12/2017 10:05AMSubject: Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?  

  
  
Are the issues you raise true of SipHash, given
  that a prime motivator for its design was generating hash tables
  for short inputs while being secure against hash flooding attacks?
  It achieves this with the performance of a portable C
  implementation the order of four times faster than MD5, and not
  much slower than other modern hash algorithms.I'd have thought the main thing to consider is whether or not
  there is any practical way a hash flooding attack could be used
  against OpenSSL's hash tables, and it sounds like there isn't. In
  that case, the fastest algorithm for the usage patterns would be
  best.Regards,    jjfOn 11/01/2017 22:25, Peter Waltenberg
  wrote:And the reason I said
you certainly don't
need a keyed hash ?Behaviour of the hash function
will
change with key and in some cases performance would degenerate
to that
of a linked list. (Ouch). And since the obvious thing to do is
use a random
key, OpenSSL's performance would get *very* erratic.Simpler functions than
cryptographic
hashes will almost certainly yield better results here. I note
someone
further up the thread someone else has pointed that out. PeterFrom:      
 "Salz, Rich"
<rs...@akamai.com>  To:      
 "openssl-dev@openssl.org"<openssl-dev@openssl.org>  Date:      
         11/01/2017 13:14  Subject:    
   Re: [openssl-dev]
use SIPhash for OPENSSL_LH_strhash?  Sent by:    
   "openssl-dev"
<openssl-dev-boun...@openssl.org>The needs for OpenSSL's LHASH are exactly what
  SipHash
  was designed for: fast on short strings.  OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5
  code is commented
  out.  Yes, performance tests would greatly inform the decision.-- J. J. FarrellNot speaking for Oracle  

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[J. J. Farrell]

Are the issues you raise true of SipHash, given that a prime motivator 
for its design was generating hash tables for short inputs while being 
secure against hash flooding attacks? It achieves this with the 
performance of a portable C implementation the order of four times 
faster than MD5, and not much slower than other modern hash algorithms.


I'd have thought the main thing to consider is whether or not there is 
any practical way a hash flooding attack could be used against OpenSSL's 
hash tables, and it sounds like there isn't. In that case, the fastest 
algorithm for the usage patterns would be best.


Regards,
  jjf

On 11/01/2017 22:25, Peter Waltenberg wrote:

And the reason I said you certainly don't need a keyed hash ?

Behaviour of the hash function will change with key and in some cases 
performance would degenerate to that of a linked list. (Ouch). And 
since the obvious thing to do is use a random key, OpenSSL's 
performance would get *very* erratic.


Simpler functions than cryptographic hashes will almost certainly 
yield better results here. I note someone further up the thread 
someone else has pointed that out.


Peter

From: "Salz, Rich" <rs...@akamai.com>
To: "openssl-dev@openssl.org" <openssl-dev@openssl.org>
Date: 11/01/2017 13:14
Subject: Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?
Sent by: "openssl-dev" <openssl-dev-boun...@openssl.org>


The needs for OpenSSL's LHASH are exactly what SipHash was designed 
for: fast on short strings.
OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 code is 
commented out.

Yes, performance tests would greatly inform the decision.


--
J. J. Farrell
Not speaking for Oracle

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Peter Waltenberg]

And the reason I said you certainly don't need a keyed hash ?

Behaviour of the hash function will change with key and in some cases 
performance would degenerate to that of a linked list. (Ouch). And since 
the obvious thing to do is use a random key, OpenSSL's performance would 
get *very* erratic.

Simpler functions than cryptographic hashes will almost certainly yield 
better results here. I note someone further up the thread someone else has 
pointed that out. 

Peter




From:   "Salz, Rich" <rs...@akamai.com>
To: "openssl-dev@openssl.org" <openssl-dev@openssl.org>
Date:   11/01/2017 13:14
Subject:    Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?
Sent by:"openssl-dev" <openssl-dev-boun...@openssl.org>



The needs for OpenSSL's LHASH are exactly what SipHash was designed for: 
fast on short strings.
OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 code is 
commented out.
Yes, performance tests would greatly inform the decision.
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Short, Todd]

I’d be doing it in a manner similar to Poly1305, since that’s a fresh memory… 
it shouldn’t take long.
--
-Todd Short
// tsh...@akamai.com
// "One if by land, two if by sea, three if by the Internet."

On Jan 11, 2017, at 9:44 AM, Richard Levitte 
> wrote:

Can we look forward to a github PR?

In message 
<97d0be2d-11c6-4d01-9a5d-faccc5b27...@akamai.com>
 on Tue, 10 Jan 2017 22:42:17 +, "Short, Todd" 
> said:

tshort> I think I might have an init/update/final version of siphash24 lying
tshort> around somewhere that would be compatible with OpenSSL’s EVP_PKEY
tshort> mechanism (similar to Poly1305, in that it needs a key).
tshort> --
tshort> -Todd Short
tshort> // tsh...@akamai.com
tshort> // "One if by land, two if by sea, three if by the Internet."
tshort>
tshort> On Jan 10, 2017, at 4:55 PM, Richard Levitte 
>
tshort> wrote:
tshort>
tshort>
tshort>
tshort>
tshort> Benjamin Kaduk > skrev: 
(10 januari 2017
tshort> 20:19:21 CET)
tshort>
tshort> On 01/10/2017 12:31 PM, Richard Levitte wrote:
tshort>
tshort>
tshort> Benjamin Kaduk 
> skrev: (10 januari 2017
tshort> 18:48:32
tshort>
tshort>
tshort> CET)
tshort>
tshort> On 01/09/2017 10:05 PM, Salz, Rich wrote:
tshort>
tshort> Should we move to using SIPHash for the default string
tshort> hashing
tshort> function in OpenSSL? It’s now in the kernel
tshort> https://lkml.org/lkml/2017/1/9/619
tshort>
tshort>
tshort>
tshort> Heck, yes!
tshort> -Ben
tshort>
tshort>
tshort> I fail to see what that would give us. OPENSSL_LH_strhash
tshort> () is used
tshort>
tshort>
tshort> to get a reasonable index for LHASH entries. Also SIPhash
tshort> gives at
tshort> least 64 bits results, do we really expect to see large enough
tshort> hash
tshort> tables to warrant that?
tshort>
tshort>
tshort>
tshort>
tshort> We don't need to use the full output width of a good hash
tshort> function.
tshort>
tshort> My main point is, "why would we want to ignore the last 20
tshort> years of
tshort> advancement in hash function research?" Section 7 of the
tshort> siphash paper
tshort> (https://131002.net/siphash/siphash.pdf) explicitly talks
tshort> about using
tshort> it
tshort> for hash tables, including using hash table indices H(m) mod
tshort> l.
tshort>
tshort>
tshort> I agree with the advice when one can expect huge tables. The
tshort> tables we handle are pretty small (I think, please correct me if
tshort> I'm wrong) and would in all likelihood not benefit very much if at
tshort> all from SIPhash's relative safety.
tshort>
tshort> Of course, one can ask the question if someone uses LHASH as a
tshort> general purpose hash table implementation rather than just for the
tshort> stuff OpenSSL. Frankly, I would probably look at a dedicated hash
tshort> table library first...
tshort>
tshort> Cheers
tshort> Richard
tshort> --
tshort> Sent from my Android device with K-9 Mail. Please excuse my
tshort> brevity.
tshort> --
tshort> openssl-dev mailing list
tshort> To unsubscribe:
tshort> https://mta.openssl.org/mailman/listinfo/openssl-dev
tshort>
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Salz, Rich]

> Is there really no use of LHASH tables in OpenSSL where an attacker
> attempting a DoS attack can control the contents of the tables?

The only use of LHASH is in SSL_SESSION and X509_NAME, which use their own 
hashing functions, and are only used after the session and/or certs have been 
cryptographically verified.

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

Can we look forward to a github PR?

In message <97d0be2d-11c6-4d01-9a5d-faccc5b27...@akamai.com> on Tue, 10 Jan 
2017 22:42:17 +, "Short, Todd"  said:

tshort> I think I might have an init/update/final version of siphash24 lying
tshort> around somewhere that would be compatible with OpenSSL’s EVP_PKEY
tshort> mechanism (similar to Poly1305, in that it needs a key).
tshort> --
tshort> -Todd Short
tshort> // tsh...@akamai.com
tshort> // "One if by land, two if by sea, three if by the Internet."
tshort> 
tshort> On Jan 10, 2017, at 4:55 PM, Richard Levitte 
tshort> wrote:
tshort> 
tshort> 
tshort> 
tshort> 
tshort> Benjamin Kaduk  skrev: (10 januari 2017
tshort> 20:19:21 CET)
tshort> 
tshort> On 01/10/2017 12:31 PM, Richard Levitte wrote:
tshort> 
tshort> 
tshort> Benjamin Kaduk  skrev: (10 januari 2017
tshort> 18:48:32
tshort> 
tshort> 
tshort> CET)
tshort> 
tshort> On 01/09/2017 10:05 PM, Salz, Rich wrote:
tshort> 
tshort> Should we move to using SIPHash for the default string
tshort> hashing
tshort> function in OpenSSL? It’s now in the kernel
tshort> https://lkml.org/lkml/2017/1/9/619
tshort> 
tshort> 
tshort> 
tshort> Heck, yes!
tshort> -Ben
tshort> 
tshort> 
tshort> I fail to see what that would give us. OPENSSL_LH_strhash
tshort> () is used
tshort> 
tshort> 
tshort> to get a reasonable index for LHASH entries. Also SIPhash
tshort> gives at
tshort> least 64 bits results, do we really expect to see large enough
tshort> hash
tshort> tables to warrant that?
tshort> 
tshort> 
tshort> 
tshort> 
tshort> We don't need to use the full output width of a good hash
tshort> function.
tshort> 
tshort> My main point is, "why would we want to ignore the last 20
tshort> years of
tshort> advancement in hash function research?" Section 7 of the
tshort> siphash paper
tshort> (https://131002.net/siphash/siphash.pdf) explicitly talks
tshort> about using
tshort> it
tshort> for hash tables, including using hash table indices H(m) mod
tshort> l.
tshort> 
tshort> 
tshort> I agree with the advice when one can expect huge tables. The
tshort> tables we handle are pretty small (I think, please correct me if
tshort> I'm wrong) and would in all likelihood not benefit very much if at
tshort> all from SIPhash's relative safety.
tshort> 
tshort> Of course, one can ask the question if someone uses LHASH as a
tshort> general purpose hash table implementation rather than just for the
tshort> stuff OpenSSL. Frankly, I would probably look at a dedicated hash
tshort> table library first...
tshort> 
tshort> Cheers
tshort> Richard
tshort> --
tshort> Sent from my Android device with K-9 Mail. Please excuse my
tshort> brevity.
tshort> --
tshort> openssl-dev mailing list
tshort> To unsubscribe:
tshort> https://mta.openssl.org/mailman/listinfo/openssl-dev
tshort> 
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

A note: I have absolutely nothing against the addition of SIPhash in
our collection of hash algos.  My scepticism was only in regards to
using it as a string hasher for our hash tables indexes.

Cheers,
Richard

In message <20170111.153458.1623912899597806811.levi...@openssl.org> on Wed, 11 
Jan 2017 15:34:58 +0100 (CET), Richard Levitte  said:

levitte> In message 
<1e19cdfea8224717b3eee11e2d8ac...@usma1ex-dag1mb1.msg.corp.akamai.com> on Wed, 
11 Jan 2017 03:13:39 +, "Salz, Rich"  said:
levitte> 
levitte> rsalz> The needs for OpenSSL's LHASH are exactly what SipHash was 
designed for: fast on short strings.
levitte> rsalz> OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 
code is commented out.
levitte> rsalz> Yes, performance tests would greatly inform the decision.
levitte> 
levitte> Done, using the reference siphash implementation.
levitte> 
levitte> https://github.com/levitte/openssl/tree/test-string-hashes
levitte> 
levitte> A run on my laptop gave these results:
levitte> 
levitte> : ; ./util/shlib_wrap.sh apps/openssl speed siphash lhash
levitte> Doing lhash for 3s on 16 size blocks: 27635188 lhash's in 3.00s
levitte> Doing lhash for 3s on 64 size blocks: 6934726 lhash's in 3.00s
levitte> Doing lhash for 3s on 256 size blocks: 1698489 lhash's in 3.00s
levitte> Doing lhash for 3s on 1024 size blocks: 431185 lhash's in 3.00s
levitte> Doing lhash for 3s on 8192 size blocks: 53868 lhash's in 3.00s
levitte> Doing lhash for 3s on 16384 size blocks: 27041 lhash's in 3.00s
levitte> Doing siphash for 3s on 16 size blocks: 22488748 siphash's in 3.00s
levitte> Doing siphash for 3s on 64 size blocks: 10485674 siphash's in 3.00s
levitte> Doing siphash for 3s on 256 size blocks: 3320898 siphash's in 3.00s
levitte> Doing siphash for 3s on 1024 size blocks: 894647 siphash's in 3.00s
levitte> Doing siphash for 3s on 8192 size blocks: 114170 siphash's in 3.00s
levitte> Doing siphash for 3s on 16384 size blocks: 57151 siphash's in 3.00s
levitte> OpenSSL 1.1.1-dev  xx XXX 
levitte> built on: reproducible build, date unspecified
levitte> options:bn(64,64) rc4(16x,int) des(int) aes(partial) idea(int) 
blowfish(ptr) 
levitte> compiler: gcc -DDSO_DLFCN -DHAVE_DLFCN_H -DOPENSSL_THREADS 
-DOPENSSL_NO_STATIC_ENGINE -DOPENSSL_PIC -DOPENSSL_IA32_SSE2 
-DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM 
-DSHA256_ASM -DSHA512_ASM -DRC4_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM 
-DGHASH_ASM -DECP_NISTZ256_ASM -DPADLOCK_ASM -DPOLY1305_ASM 
-DOPENSSLDIR="\"/usr/local/ssl\"" -DENGINESDIR="\"/usr/local/lib/engines-1.1\"" 
 -DDEBUG_UNUSED -Wswitch -DPEDANTIC -pedantic -Wno-long-long -Wall 
-Wsign-compare -Wmissing-prototypes -Wshadow -Wformat -Wtype-limits -Werror 
-Wa,--noexecstack
levitte> The 'numbers' are in 1000s of bytes per second processed.
levitte> type 16 bytes 64 bytes256 bytes   1024 bytes   
8192 bytes  16384 bytes
levitte> lhash   147387.67k   147940.82k   144937.73k   147177.81k  
 147095.55k   147679.91k
levitte> siphash 119939.99k   223694.38k   283383.30k   305372.84k  
 311760.21k   312120.66k
levitte> 
levitte> So it seems that for short strings, OPENSSL_LH_strhash (*) wins some,
levitte> while siphash wins big for larger strings.
levitte> 
levitte> I have no idea how they compare with regard to distribution (which,
levitte> considering I ask for the same size output from both, should be the
levitte> main factor that affects the sensitivity to hash flooding)...
levitte> 
levitte> Our use of OPENSSL_LH_strhash() is with configuration sections and
levitte> names, ASN.1 object names and the function names in the openssl app.
levitte> All our other uses of lhash use their own hashing functions, and are
levitte> usually very short still (definitely less than 16 bytes).
levitte> 
levitte> My conclusion is that performance-wise, siphash doesn't give us any
levitte> advantage over OpenSSL_LH_strhash for our uses.
levitte> 
levitte> Cheers,
levitte> Richard
levitte> 
levitte> (*) Strictly speaking, it's a modified version that takes a length and
levitte> tolerates all 8-bit bytes, including 0x00.
levitte> 
levitte> -- 
levitte> Richard Levitte levi...@openssl.org
levitte> OpenSSL Project http://www.openssl.org/~levitte/
levitte> -- 
levitte> openssl-dev mailing list
levitte> To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-dev
levitte> 
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

In message 
<1e19cdfea8224717b3eee11e2d8ac...@usma1ex-dag1mb1.msg.corp.akamai.com> on Wed, 
11 Jan 2017 03:13:39 +, "Salz, Rich"  said:

rsalz> The needs for OpenSSL's LHASH are exactly what SipHash was designed for: 
fast on short strings.
rsalz> OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 code is 
commented out.
rsalz> Yes, performance tests would greatly inform the decision.

Done, using the reference siphash implementation.

https://github.com/levitte/openssl/tree/test-string-hashes

A run on my laptop gave these results:

: ; ./util/shlib_wrap.sh apps/openssl speed siphash lhash
Doing lhash for 3s on 16 size blocks: 27635188 lhash's in 3.00s
Doing lhash for 3s on 64 size blocks: 6934726 lhash's in 3.00s
Doing lhash for 3s on 256 size blocks: 1698489 lhash's in 3.00s
Doing lhash for 3s on 1024 size blocks: 431185 lhash's in 3.00s
Doing lhash for 3s on 8192 size blocks: 53868 lhash's in 3.00s
Doing lhash for 3s on 16384 size blocks: 27041 lhash's in 3.00s
Doing siphash for 3s on 16 size blocks: 22488748 siphash's in 3.00s
Doing siphash for 3s on 64 size blocks: 10485674 siphash's in 3.00s
Doing siphash for 3s on 256 size blocks: 3320898 siphash's in 3.00s
Doing siphash for 3s on 1024 size blocks: 894647 siphash's in 3.00s
Doing siphash for 3s on 8192 size blocks: 114170 siphash's in 3.00s
Doing siphash for 3s on 16384 size blocks: 57151 siphash's in 3.00s
OpenSSL 1.1.1-dev  xx XXX 
built on: reproducible build, date unspecified
options:bn(64,64) rc4(16x,int) des(int) aes(partial) idea(int) 
blowfish(ptr) 
compiler: gcc -DDSO_DLFCN -DHAVE_DLFCN_H -DOPENSSL_THREADS 
-DOPENSSL_NO_STATIC_ENGINE -DOPENSSL_PIC -DOPENSSL_IA32_SSE2 
-DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM 
-DSHA256_ASM -DSHA512_ASM -DRC4_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM 
-DGHASH_ASM -DECP_NISTZ256_ASM -DPADLOCK_ASM -DPOLY1305_ASM 
-DOPENSSLDIR="\"/usr/local/ssl\"" -DENGINESDIR="\"/usr/local/lib/engines-1.1\"" 
 -DDEBUG_UNUSED -Wswitch -DPEDANTIC -pedantic -Wno-long-long -Wall 
-Wsign-compare -Wmissing-prototypes -Wshadow -Wformat -Wtype-limits -Werror 
-Wa,--noexecstack
The 'numbers' are in 1000s of bytes per second processed.
type 16 bytes 64 bytes256 bytes   1024 bytes   8192 
bytes  16384 bytes
lhash   147387.67k   147940.82k   144937.73k   147177.81k   
147095.55k   147679.91k
siphash 119939.99k   223694.38k   283383.30k   305372.84k   
311760.21k   312120.66k

So it seems that for short strings, OPENSSL_LH_strhash (*) wins some,
while siphash wins big for larger strings.

I have no idea how they compare with regard to distribution (which,
considering I ask for the same size output from both, should be the
main factor that affects the sensitivity to hash flooding)...

Our use of OPENSSL_LH_strhash() is with configuration sections and
names, ASN.1 object names and the function names in the openssl app.
All our other uses of lhash use their own hashing functions, and are
usually very short still (definitely less than 16 bytes).

My conclusion is that performance-wise, siphash doesn't give us any
advantage over OpenSSL_LH_strhash for our uses.

Cheers,
Richard

(*) Strictly speaking, it's a modified version that takes a length and
tolerates all 8-bit bytes, including 0x00.

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OpenSSL Project http://www.openssl.org/~levitte/
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

In message <001901d26bed$d3746ed0$7a5d4c70$@sa...@free.fr> on Wed, 11 Jan 2017 
10:33:53 +0100, "Michel"  said:

michel.sales> And what about using FNV or CityHash ?
michel.sales> 
michel.sales> 
https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function

I'm a little worried about the zero hash value issue mentioned here:

https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#Non-cryptographic_hash

michel.sales> https://en.wikipedia.org/wiki/CityHash

Google has replaced that with FarmHash according to that page...

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Michel]

And what about using FNV or CityHash ?

https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
https://en.wikipedia.org/wiki/CityHash


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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Tomas Mraz]

On Wed, 2017-01-11 at 03:13 +, Salz, Rich wrote:
> The needs for OpenSSL's LHASH are exactly what SipHash was designed
> for: fast on short strings.
> OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 code is
> commented out.
> Yes, performance tests would greatly inform the decision.

+1

Is there really no use of LHASH tables in OpenSSL where an attacker
attempting a DoS attack can control the contents of the tables? If you
are reasonably sure that there is no such occurrence or that the number
of entries attacker can insert into such table is severally limited by
other means then perhaps it really makes no sense to replace the
existing algorithm. But we need to know this first.

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No matter how far down the wrong road you've gone, turn back.
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(You'll never know whether the road is wrong though.)

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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Salz, Rich]

The needs for OpenSSL's LHASH are exactly what SipHash was designed for: fast 
on short strings.
OpenSSL's hash currently *does not* call MD5 or SHA1; the MD5 code is commented 
out.
Yes, performance tests would greatly inform the decision.
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Peter Waltenberg]

Reality check

Others have pointed this out but I don't think it's making it through. 
LHash doesn't need a cryptographic hash and it doesn't have security 
implications. It certainly doesn't need a keyed hash.

LHash does need to be something that's good at distinguishing short text 
strings, that's not necessarilly the same thing as a good cryptographic 
hash, and possibly it's exactly the opposite thing due to the limitted 
incoming symbol space (ascii text).
About the only thing LHash needs is high performance in it's use area. I'd 
suspect that switching MD5 to SHA-1 in the existing algorithm would get 
you that simply because SHA-1 is asm optimized on most platforms now and 
MD5 typically isn't.
I'd suggest that anyone wishing to change this should at least have to 
demonstrate improved performance in the OpenSSL use case before it's 
accepted.

Peter



From:   "Short, Todd" <tsh...@akamai.com>
To: "openssl-dev@openssl.org" <openssl-dev@openssl.org>
Date:   11/01/2017 08:42
Subject:    Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?
Sent by:"openssl-dev" <openssl-dev-boun...@openssl.org>



I think I might have an init/update/final version of siphash24 lying 
around somewhere that would be compatible with OpenSSL’s EVP_PKEY 
mechanism (similar to Poly1305, in that it needs a key).
--
-Todd Short
// tsh...@akamai.com
// "One if by land, two if by sea, three if by the Internet."

On Jan 10, 2017, at 4:55 PM, Richard Levitte <levi...@openssl.org> wrote:



Benjamin Kaduk <bka...@akamai.com> skrev: (10 januari 2017 20:19:21 CET)
On 01/10/2017 12:31 PM, Richard Levitte wrote:

Benjamin Kaduk <bka...@akamai.com> skrev: (10 januari 2017 18:48:32
CET)
On 01/09/2017 10:05 PM, Salz, Rich wrote:
Should we move to using SIPHash for the default string hashing
function in OpenSSL?  It’s now in the kernel
https://lkml.org/lkml/2017/1/9/619

Heck, yes!
-Ben
I fail to see what that would give us. OPENSSL_LH_strhash() is used
to get a reasonable index for LHASH entries. Also SIPhash gives at
least 64 bits results, do we really expect to see large enough hash
tables to warrant that? 


We don't need to use the full output width of a good hash function.

My main point is, "why would we want to ignore the last 20 years of
advancement in hash function research?"  Section 7 of the siphash paper
(https://131002.net/siphash/siphash.pdf) explicitly talks about using
it
for hash tables, including using hash table indices H(m) mod l.

I agree with the advice when one can expect huge tables. The tables we 
handle are pretty small (I think, please correct me if I'm wrong) and 
would in all likelihood not benefit very much if at all from SIPhash's 
relative safety. 

Of course, one can ask the question if someone uses LHASH as a general 
purpose hash table implementation rather than just for the stuff OpenSSL. 
Frankly, I would probably look at a dedicated hash table library first... 

Cheers 
Richard 
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Short, Todd]

I think I might have an init/update/final version of siphash24 lying around 
somewhere that would be compatible with OpenSSL’s EVP_PKEY mechanism (similar 
to Poly1305, in that it needs a key).
--
-Todd Short
// tsh...@akamai.com
// "One if by land, two if by sea, three if by the Internet."

On Jan 10, 2017, at 4:55 PM, Richard Levitte 
> wrote:



Benjamin Kaduk > skrev: (10 januari 
2017 20:19:21 CET)
On 01/10/2017 12:31 PM, Richard Levitte wrote:

Benjamin Kaduk > skrev: (10 januari 
2017 18:48:32
CET)
On 01/09/2017 10:05 PM, Salz, Rich wrote:
Should we move to using SIPHash for the default string hashing
function in OpenSSL?  It’s now in the kernel
https://lkml.org/lkml/2017/1/9/619

Heck, yes!
-Ben
I fail to see what that would give us. OPENSSL_LH_strhash() is used
to get a reasonable index for LHASH entries. Also SIPhash gives at
least 64 bits results, do we really expect to see large enough hash
tables to warrant that?


We don't need to use the full output width of a good hash function.

My main point is, "why would we want to ignore the last 20 years of
advancement in hash function research?"  Section 7 of the siphash paper
(https://131002.net/siphash/siphash.pdf) explicitly talks about using
it
for hash tables, including using hash table indices H(m) mod l.

I agree with the advice when one can expect huge tables. The tables we handle 
are pretty small (I think, please correct me if I'm wrong) and would in all 
likelihood not benefit very much if at all from SIPhash's relative safety.

Of course, one can ask the question if someone uses LHASH as a general purpose 
hash table implementation rather than just for the stuff OpenSSL. Frankly, I 
would probably look at a dedicated hash table library first...

Cheers
Richard
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

Benjamin Kaduk  skrev: (10 januari 2017 20:19:21 CET)
>On 01/10/2017 12:31 PM, Richard Levitte wrote:
>>
>> Benjamin Kaduk  skrev: (10 januari 2017 18:48:32
>CET)
>>> On 01/09/2017 10:05 PM, Salz, Rich wrote:
 Should we move to using SIPHash for the default string hashing
 function in OpenSSL?  It’s now in the kernel
 https://lkml.org/lkml/2017/1/9/619

>>> Heck, yes!
>>> -Ben
>> I fail to see what that would give us. OPENSSL_LH_strhash() is used
>to get a reasonable index for LHASH entries. Also SIPhash gives at
>least 64 bits results, do we really expect to see large enough hash
>tables to warrant that? 
>>
>
>We don't need to use the full output width of a good hash function.
>
>My main point is, "why would we want to ignore the last 20 years of
>advancement in hash function research?"  Section 7 of the siphash paper
>(https://131002.net/siphash/siphash.pdf) explicitly talks about using
>it
>for hash tables, including using hash table indices H(m) mod l.

I agree with the advice when one can expect huge tables. The tables we handle 
are pretty small (I think, please correct me if I'm wrong) and would in all 
likelihood not benefit very much if at all from SIPhash's relative safety. 

Of course, one can ask the question if someone uses LHASH as a general purpose 
hash table implementation rather than just for the stuff OpenSSL. Frankly, I 
would probably look at a dedicated hash table library first... 

Cheers 
Richard 
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Blumenthal, Uri - 0553 - MITLL]

We don’t need the full output width of a good hash function, but for _this_ 
purpose (as far as I understand) we don’t need the strength of a good hash 
function either – and we surely don’t need the unnecessary performance hit of a 
good hash where we don’t need a good hash.

 

Or am I missing something?

— 

Regards,

Uri

 

 

On 1/10/17, 2:19 PM, "openssl-dev on behalf of Benjamin Kaduk" 
 wrote:

 

On 01/10/2017 12:31 PM, Richard Levitte wrote:

 
Benjamin Kaduk  skrev: (10 januari 2017 18:48:32 CET)
On 01/09/2017 10:05 PM, Salz, Rich wrote:
Should we move to using SIPHash for the default string hashing
function in OpenSSL?  It’s now in the kernel
https://lkml.org/lkml/2017/1/9/619
 
Heck, yes! 
-Ben
I fail to see what that would give us. OPENSSL_LH_strhash() is used to get a 
reasonable index for LHASH entries. Also SIPhash gives at least 64 bits 
results, do we really expect to see large enough hash tables to warrant that? 
 

We don't need to use the full output width of a good hash function.


My main point is, "why would we want to ignore the last 20 years of advancement 
in hash function research?"  Section 7 of the siphash paper 
(https://131002.net/siphash/siphash.pdf) explicitly talks about using it for 
hash tables, including using hash table indices H(m) mod l.

-Ben



smime.p7s
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Benjamin Kaduk]

On 01/10/2017 12:31 PM, Richard Levitte wrote:
>
> Benjamin Kaduk  skrev: (10 januari 2017 18:48:32 CET)
>> On 01/09/2017 10:05 PM, Salz, Rich wrote:
>>> Should we move to using SIPHash for the default string hashing
>>> function in OpenSSL?  It’s now in the kernel
>>> https://lkml.org/lkml/2017/1/9/619
>>>
>> Heck, yes!
>> -Ben
> I fail to see what that would give us. OPENSSL_LH_strhash() is used to get a 
> reasonable index for LHASH entries. Also SIPhash gives at least 64 bits 
> results, do we really expect to see large enough hash tables to warrant that? 
>

We don't need to use the full output width of a good hash function.

My main point is, "why would we want to ignore the last 20 years of
advancement in hash function research?"  Section 7 of the siphash paper
(https://131002.net/siphash/siphash.pdf) explicitly talks about using it
for hash tables, including using hash table indices H(m) mod l.

-Ben
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Richard Levitte]

Benjamin Kaduk  skrev: (10 januari 2017 18:48:32 CET)
>On 01/09/2017 10:05 PM, Salz, Rich wrote:
>>
>> Should we move to using SIPHash for the default string hashing
>> function in OpenSSL?  It’s now in the kernel
>> https://lkml.org/lkml/2017/1/9/619
>>
>
>>
>> Overview at https://131002.net/siphash/
>>
>
>>
>>
>
>Instead of this?
>
>%
>
>/*-
>unsigned char b[16];
>MD5(c,strlen(c),b);
>return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24));
>*/
>
>n = 0x100;
>while (*c) {
>v = n | (*c);
>n += 0x100;
>r = (int)((v >> 2) ^ v) & 0x0f;
>ret = (ret << r) | (ret >> (32 - r));
>ret &= 0xL;
>ret ^= v * v;
>c++;
>}
>return ((ret >> 16) ^ ret);
>
>%
>
>Heck, yes!
>
>-Ben

I fail to see what that would give us. OPENSSL_LH_strhash() is used to get a 
reasonable index for LHASH entries. Also SIPhash gives at least 64 bits 
results, do we really expect to see large enough hash tables to warrant that? 

Cheers 
Richard 
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Re: [openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Benjamin Kaduk]

On 01/09/2017 10:05 PM, Salz, Rich wrote:
>
> Should we move to using SIPHash for the default string hashing
> function in OpenSSL?  It’s now in the kernel
> https://lkml.org/lkml/2017/1/9/619
> 
>
> Overview at https://131002.net/siphash/
> 
>
>

Instead of this?

%

/*-
unsigned char b[16];
MD5(c,strlen(c),b);
return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24));
*/

n = 0x100;
while (*c) {
v = n | (*c);
n += 0x100;
r = (int)((v >> 2) ^ v) & 0x0f;
ret = (ret << r) | (ret >> (32 - r));
ret &= 0xL;
ret ^= v * v;
c++;
}
return ((ret >> 16) ^ ret);

%

Heck, yes!

-Ben
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[openssl-dev] use SIPhash for OPENSSL_LH_strhash?

[Salz, Rich]

Should we move to using SIPHash for the default string hashing function in 
OpenSSL?  It's now in the kernel https://lkml.org/lkml/2017/1/9/619
Overview at https://131002.net/siphash/


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