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Multos Trust Anchor and maximum key size for ECC

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Total Posts: 10

Joined 2018-12-13

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Dear all,

I would like to use different curves (domain parameters) from https://safecurves.cr.yp.to/ on Multos Trust Anchor. I succeed to support Curve25519 (256 bit) but I failed for M-383, Curve383187 and M-511.

However the chip is equiped with infineon crypt@2304T I was assumed to be able to reach 521 bit.

Is this a known limitation? Is it possible using API to know the max key size supported? Is there another way to know that?

Best regards,

     
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Total Posts: 10

Joined 2018-12-13

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Dear all,

I also failed to use curves under whose parameter are smaller than 192 bits like secp160r1, secp160k1 (it might be an issue for those two of N length) or secp128r1 or secp112r1…

Is this a known limitation?

     
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Total Posts: 82

Joined 2012-02-21

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Hi Damien,

The prime length range supported is 21 - 66 bytes inclusive. That rules out the smaller curves you tried.

Domain parameters must also be consistent with Short Weierstrass equation representation (y^2 = x^3 + A.x +B). Perhaps that is why some of the others didn’t work?

Chris.

     
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Total Posts: 10

Joined 2018-12-13

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Dear Chris,

You are right for the smaller ones.

You are also right for M511, Curve383187 and M383 since they were Montgomery curves.

I have tried and I have succeeded with secp521r1 ...

It is a pity since the safe curves are not on Short Weierstrass curve https://safecurves.cr.yp.to/


Best regards,
Damien