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Question about ctr mode 3des-ede IV len

Started by"Longpeng (Mike)" <longpeng2@huawei.com>
First post2016-12-07 13:50 +0100
Last post2016-12-08 12:40 +0100
Articles 5 — 3 participants

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  Question about ctr mode 3des-ede IV len "Longpeng (Mike)" <longpeng2@huawei.com> - 2016-12-07 13:50 +0100
    Re: Question about ctr mode 3des-ede IV len Herbert Xu <herbert@gondor.apana.org.au> - 2016-12-08 10:10 +0100
      Re: Question about ctr mode 3des-ede IV len "Longpeng (Mike)" <longpeng2@huawei.com> - 2016-12-08 10:20 +0100
    Re: Question about ctr mode 3des-ede IV len Jussi Kivilinna <jussi.kivilinna@iki.fi> - 2016-12-08 12:20 +0100
      Re: Question about ctr mode 3des-ede IV len "Longpeng (Mike)" <longpeng2@huawei.com> - 2016-12-08 12:40 +0100

#1537722 — Question about ctr mode 3des-ede IV len

From"Longpeng (Mike)" <longpeng2@huawei.com>
Date2016-12-07 13:50 +0100
SubjectQuestion about ctr mode 3des-ede IV len
Message-ID<sLJPz-a6-1@gated-at.bofh.it>
Hi Jussi and Herbert,

I saw serveral des3-ede testcases(in crypto/testmgr.h) has 16-bytes IV, and the
libgcrypt/nettle/RFC1851 said the IV-len is 8-bytes.

Would you please tell me why these testcases has 16-bytes IV ?

Thank you. :)

-- 
Regards,
Longpeng(Mike)

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#1538392

FromHerbert Xu <herbert@gondor.apana.org.au>
Date2016-12-08 10:10 +0100
Message-ID<sM2Se-4hp-15@gated-at.bofh.it>
In reply to#1537722
On Wed, Dec 07, 2016 at 08:43:16PM +0800, Longpeng (Mike) wrote:
> Hi Jussi and Herbert,
> 
> I saw serveral des3-ede testcases(in crypto/testmgr.h) has 16-bytes IV, and the
> libgcrypt/nettle/RFC1851 said the IV-len is 8-bytes.
> 
> Would you please tell me why these testcases has 16-bytes IV ?

I think they were automatically generated.  Only the first eight
bytes are actually used so the IV size is still 8.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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#1538396

From"Longpeng (Mike)" <longpeng2@huawei.com>
Date2016-12-08 10:20 +0100
Message-ID<sM31T-4kE-9@gated-at.bofh.it>
In reply to#1538392

On 2016/12/8 17:04, Herbert Xu wrote:

> On Wed, Dec 07, 2016 at 08:43:16PM +0800, Longpeng (Mike) wrote:
>> Hi Jussi and Herbert,
>>
>> I saw serveral des3-ede testcases(in crypto/testmgr.h) has 16-bytes IV, and the
>> libgcrypt/nettle/RFC1851 said the IV-len is 8-bytes.
>>
>> Would you please tell me why these testcases has 16-bytes IV ?
> 
> I think they were automatically generated.  Only the first eight
> bytes are actually used so the IV size is still 8.
> 
> Cheers,


Cool, thank you very much! :)

-- 
Regards,
Longpeng(Mike)

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#1538437

FromJussi Kivilinna <jussi.kivilinna@iki.fi>
Date2016-12-08 12:20 +0100
Message-ID<sM4U2-5tG-5@gated-at.bofh.it>
In reply to#1537722
Hello,

07.12.2016, 14:43, Longpeng (Mike) kirjoitti:
> Hi Jussi and Herbert,
> 
> I saw serveral des3-ede testcases(in crypto/testmgr.h) has 16-bytes IV, and the
> libgcrypt/nettle/RFC1851 said the IV-len is 8-bytes.
> 
> Would you please tell me why these testcases has 16-bytes IV ?

Because I used same tool to create test-vectors which I had previously used to create AES/Camellia/Serpent/Twofish test-vectors. So, I must have forgotten to change 16-byte IV generation to 8 bytes and thus those testcases in crypto/testmgr.h have wrong length. The extra trailing 8 bytes are not used and can be removed.

-Jussi

> 
> Thank you. :)
> 

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#1538455

From"Longpeng (Mike)" <longpeng2@huawei.com>
Date2016-12-08 12:40 +0100
Message-ID<sM5do-5A5-25@gated-at.bofh.it>
In reply to#1538437
Hi Jussi,

On 2016/12/7 21:15, Jussi Kivilinna wrote:

> Hello,
> 
> 07.12.2016, 14:43, Longpeng (Mike) kirjoitti:
>> Hi Jussi and Herbert,
>>
>> I saw serveral des3-ede testcases(in crypto/testmgr.h) has 16-bytes IV, and the
>> libgcrypt/nettle/RFC1851 said the IV-len is 8-bytes.
>>
>> Would you please tell me why these testcases has 16-bytes IV ?
> 
> Because I used same tool to create test-vectors which I had previously used to create AES/Camellia/Serpent/Twofish test-vectors. So, I must have forgotten to change 16-byte IV generation to 8 bytes and thus those testcases in crypto/testmgr.h have wrong length. The extra trailing 8 bytes are not used and can be removed.
> 


Thank you very much. :)

> -Jussi
> 
>>
>> Thank you. :)
>>
> 
> .
> 


-- 
Regards,
Longpeng(Mike)

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