Re: [keyassure] Opening issue #21: "Need to specify which crypto

Martin Rex <> Wed, 02 March 2011 17:23 UTC

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From: Martin Rex <>
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To: (Phillip Hallam-Baker)
Date: Wed, 2 Mar 2011 18:24:55 +0100 (MET)
In-Reply-To: <> from "Phillip Hallam-Baker" at Mar 2, 11 12:04:56 pm
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Subject: Re: [keyassure] Opening issue #21: "Need to specify which crypto
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Phillip Hallam-Baker wrote:
> The use of MD2 in a self signed cert has little risk as far as use of
> the cert itself goes since it only serves as proof of possession which
> is only relevant when the browser provider chooses to install it in
> the browser.

In the universe where I live, there exist collision attacks against MD2.

So an RSA-key for which a PKCS#1 encrypted MD2 signature has been
published is a real security problem and ought to have been discarded
long ago.

Else someone could try to use the preimage attack to issue himself
an intermediate CA cert under such a root cert, reusing the md2-based
signature on the RootCA cert.

I would REALLY like to kill md2withRsaEncryption as a digital
signature algorithm from our PKI implementation, like I did
with all of md4-based digital signature algorithms.

Getting rid of "tainted" RSA keys is also important.

Why do you think that FIPS 186-3 says that you are not allowed
to use an RSA keypair for both PKCS-v1.5 and PKCS-PSS signatures?
Because you "taint" your RSA key on the first time that you use it
for a weak scheme.