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Today's Topics:
1. ECDHE Shared Secret is computed differently (T V LIJIN (EXT))
2. Re: ECDHE Shared Secret is computed differently (Brian D.)
3. How does the bignum.c works? (Shariful Alam)
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Message: 1
Date: Thu, 24 Jun 2021 13:35:03 +0000
From: "T V LIJIN (EXT)" <lijin.tv@kone.com>
To: "mbed-tls@lists.trustedfirmware.org"
<mbed-tls@lists.trustedfirmware.org>
Subject: [mbed-tls] ECDHE Shared Secret is computed differently
Message-ID:
<AS8PR07MB8006A77D2451AD93FAFDA3D8FE079@AS8PR07MB8006.eurprd07.prod.outlook.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello ,
We are trying to perform an ECDHE key exchange between two devices running on different platforms.[one on Linux and another on RTOS]
Both the devices use the same code to compute the ECDHE shared secret. The peer public parameters are exchanged in the base64 format and passed to the functions correctly , but the final shared secret computed seems to be different on both ends.
We have tested the same source code on Visual studio and found working.
I have attached the source files
Could you please comment on why the computed shared secret are different on both the ends?
Thanks,
LIJIN T V
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Message: 2
Date: Thu, 24 Jun 2021 16:44:18 +0200 (CEST)
From: "Brian D." <brian_d@tutanota.com>
To: "T V LIJIN (EXT)" <lijin.tv@kone.com>
Cc: "mbed-tls@lists.trustedfirmware.org"
<mbed-tls@lists.trustedfirmware.org>
Subject: Re: [mbed-tls] ECDHE Shared Secret is computed differently
Message-ID: <McyTdCH--3-2@tutanota.com>
Content-Type: text/plain; charset=UTF-8
Hi Linjin,
I am not part of the mbed-tls staff but I developed a lot with mbed library and I had your same problem. Try to check the byte order, I had issues when computing the shared secret because I had the little endian from the other side but mbed uses big endian.
Try to do a quick test and this could resolve your problem, let me know!
Bye,
Brian
24 giu 2021, 15:35 da mbed-tls@lists.trustedfirmware.org:
> Hello ,
> We are trying to perform an ECDHE key exchange between two devices running on different platforms.[one on Linux and another on RTOS]
> Both the devices use the same code to compute the ECDHE shared secret. The peer public parameters are exchanged in the base64 format and passed to the functions correctly , but the final shared secret computed seems to be different on both ends.
> We have tested the same source code on Visual studio and found working.
> I have attached the source files
>
> Could you please comment on why the computed shared secret are different on both the ends?
>
> Thanks,
> LIJIN T V
>
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Message: 3
Date: Thu, 24 Jun 2021 17:21:30 -0600
From: Shariful Alam <dipto181@gmail.com>
To: mbed-tls@lists.trustedfirmware.org
Subject: [mbed-tls] How does the bignum.c works?
Message-ID:
<CAA0KgGoTKuUx3YqTAY+gPEN1uuxR2FJv_1dq15U3ycPfQWe=QQ@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello,
Can someone please briefly explain how does the bignum.c library works in
terms of RSA? I understand that this is too broad a question to ask. but If
someone can briefly explain the basic working mechanism it will be a great
help.
Thanks,
Shariful
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