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<div class="">Bonjour,</div>
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<div class="">Le 22 juil. 2016 à 08:44, Gupta, Saurabh <<a href="mailto:Saurabh.Gupta@cavium.com" class="">Saurabh.Gupta@cavium.com</a>> a écrit :</div>
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<p class=""><span style="font-size: 10pt;" class=""></span><span style="font-size: 12pt;" class="">1: I didn't get it, Why this behaviour is not coming for other ciphers while doing the server/client handshake?
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<p class=""><span style="font-size: 12pt;" class="">It should fail for other ciphers also. <br class="">
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<p class=""><span style="font-size: 12pt;" class="">Ciphers: working <br class="">
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<div class="">DHE-RSA-AES128-SHA<br class="">
<div class="">ECDHE-RSA-AES256-GCM-SHA384<br class="">
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<div>Because the key exchange is performed using DHE or ECDHE here, and parameters are much smaller than your server authentication key.</div>
<div>If you configure a 16k DH group and choose to use DHE as the key exchange algorithm, you’ll surely fall under the same error.</div>
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<div class="">Ciphers: Not working<br class="">
AES128-SHA<br class="">
<span style="font-size: 12pt;" class="">AES256-SHA <br class="">
...... etc</span><br class="">
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<div>RSA key exchange.</div>
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<div class=""><span style="font-size: 12pt;" class="">2: if anyway I want to use 16k modulus, Do we have solution to avoid this issue so that it won't harm to other application or create any new attack?</span></div>
<p class="">3: ECC cipher is not my main concerned.<br class="">
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<div>You should be concerned about the security provided by your choices, and not pure raw numbers.</div>
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<span style="font-size:12pt" class="">4: I didn't face any issue like memory utilisation or CPU utilisation is more if I'm running more than one client in the case of 16k modulus.<br class="">
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<div class="">Your measuring tools are bad, change them ;)</div>
<div class="">Signing with a 16k RSA key is way slower than with a 2048bits key, and again way slower than using ECC.</div>
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<div class="">According to NIST, equivalent « security levels »:</div>
<div class="">RSA15360, DH15360, ECC512 (or 521)</div>
<div class="">RSA7680, DH7680, ECC384</div>
<div class="">RSA3072, DH3072, ECC256</div>
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<div class="">Measurements done on my machine:</div>
<div class="">Signing with ECDSA over the P521 curve is 600x faster than signing with a 15kRSA key.</div>
<div class="">Performing a key exchange with ECDH over the P521 curve is about 180x faster than decrypting with a 15k RSA key.</div>
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<div class="">Using the P384 curve and a 7kRSA key, the numbers are 180x faster and 50x faster.</div>
<div class="">Using the P256 curve and a 4kRSA key, numbers are about 90x faster for both operations.</div>
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<div class="">I don’t have any measurements for DH key exchange, but it should cost twice more than doing a private RSA operation, and also impacts the client, and when used within TLS it comes in addition to an RSA signing operation.</div>
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