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0 pointsFabHK7y ago0 comments

Filippo Valsorda had a blog post on uploading his private key (back in 2014) in which he actually publicly uploaded his private key - encrypted, that is, as it is uploaded to Keybase [1].

Of course, it goes against orthodoxy to share/upload your private key, but I'm not sure I've ever seen a good rebuttal to Filippo's post.

It seems to me though that you're reducing the entropy of your key from the 2048 bits or whatever to the entropy of your key phrase, which would normally only be some 100 or so bits (if you have a decent one) - but I'm not informed enough to judge the details. However, it seems to me that Filippo is, and he did upload his private key (encrypted) - so how bad is that, really? Anyone got some substantiated insights there?

[1] https://blog.filippo.io/on-keybase-dot-io-and-encrypted-priv...

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4 comments · 3 top-level

jwilk7y ago· 1 in thread

Security strength of RSA is much lower than the key size.

2048-bit RSA gives you only ~112 bits of security.

FabHKOP7y ago

That's very informative, thanks. So indeed, with a good passphrase the drop in security is minimal.

Leace7y ago

I wouldn't have an issue with that if it was a private subkey. You could easily revoke it and replace it in case Keybase does something weird. But giving them private keys for master/primary key is not exactly sensible.

For the record I don't have a private master key in any online connected devices. GnuPG works well in an air-gapped scenarios. Does Keybase client? Or does it require constant phoning home?

danenania7y ago

If you encrypt a private key with a secret passphrase, then upload the encrypted private key somewhere, the passphrase is essentially your new private key. As long as the passphrase has sufficient entropy, there's no meaningful drop in security with this approach.

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