Cracking a 512-bit DKIM key for less than $8 in the cloud

Post by IncRnd » Wed, Jan 08, 2025, 6:23 PM UTC

GTP wrote: post #163

dfc wrote: post #59

Earlier quoted context omitted.

You should read the blog post Prof. Green linked to. All of your questions are addressed there.

Yes, I've now read it and it answered those questions. But it also stumbled upon an easier possible solution without realizing it: if you wish to pretend you didn't send some emails, you can still claim that someone stole your password. Whether this claim will be believed or not, is independent of DKIM. Spoofing is a better excuse than a stolen password only in the case of a single email. If there's a conversation sp…

Post by wolrah » Wed, Jan 08, 2025, 6:24 PM UTC

asim wrote: post #43

I think the cynic in me says "so what" mostly because dkim as an ancient technology is hardly secure. I don't think we're any less prone to email fakery and spam. I'd be interested to see a possible new solution or a revamping of email as a protocol but that's unlikely. We're more likely to keep it like snail mail as we prioritise different forms of communication. Unfortunately nothing has beat the universal email ad…

Post by throw0101c » Wed, Jan 08, 2025, 6:32 PM UTC

daneel_w wrote: post #174

jandrese wrote: post #154

Earlier quoted context omitted.

Is there a compelling reason to use 3072 instead of 4096? If you're going to kick the can down the road you might as well put some effort into it. The difference in memory use/compute time has to be marginal at this point. It's not like the old days when jumping from 512 to 4096 made the encryption unusably slow.

There's no good reason at all, which is why RSA-3072 is the rarely seen "oddball".

    version: 3.4.0
    built on: Tue Dec  3 14:33:57 2024 UTC
    options: bn(64,64)
    compiler: /usr/bin/clang -fPIC -arch arm64 -pipe -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk -arch arm64 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk -DL_ENDIAN -DOPENSSL_PIC -D_REENTRANT -DOPENSSL_BUILDING_OPENSSL -DZLIB -DNDEBUG -I/opt/local/include -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX15.sdk
    CPUINFO: OPENSSL_armcap=0x87d
                       sign    verify    encrypt   decrypt   sign/s verify/s  encr./s  decr./s
    rsa   512 bits 0.000012s 0.000001s 0.000001s 0.000016s  80317.8 973378.4 842915.2  64470.9
    rsa  1024 bits 0.000056s 0.000003s 0.000003s 0.000060s  17752.4 381404.1 352224.8  16594.4
    rsa  2048 bits 0.000334s 0.000008s 0.000009s 0.000343s   2994.9 117811.8 113258.1   2915.6
    rsa  3072 bits 0.000982s 0.000018s 0.000019s 0.000989s   1018.4  54451.6  53334.8   1011.3
    rsa  4096 bits 0.002122s 0.000031s 0.000032s 0.002129s    471.3  31800.6  31598.7    469.8
    rsa  7680 bits 0.016932s 0.000104s 0.000107s 0.017048s     59.1   9585.7   9368.4     58.7
    rsa 15360 bits 0.089821s 0.000424s 0.000425s 0.090631s     11.1   2357.4   2355.5     11.0

Post by layer8 » Wed, Jan 08, 2025, 6:38 PM UTC

Uriopass wrote: post #195

croemer wrote: post #186

Slight change of title. The leading "How" was dropped. Original: "How We Cracked a 512-Bit DKIM Key for Less Than $8 in the Cloud"

Dropping the How is part of Hackernews guidelines

Post by bluGill » Wed, Jan 08, 2025, 6:45 PM UTC

tptacek wrote: post #96

bluGill wrote: post #57

Earlier quoted context omitted.

RSA 2048 isn't broken, but experts consider it a matter of time. How long I don't know, but since the attacks are known (prime numbers) someone (read not me) can make an estimate with error bars that are concerning enough to consider it as good as broken.

What expert considers it a matter of time before 2048 is broken? 2048 is 112-bit-equivalent security.