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When they started asking me for my private key and claiming it'll be secure because it's "encrypted" that raised a red flag for me. Then I found out that they'

by Leace 8y ago

When they started asking me for my private key and claiming it'll be secure because it's "encrypted" that raised a red flag for me. Then I found out that they're not using popular and audited libraries like OpenPGPjs instead... writing their own!

oedmarap 8y ago
I second this. Would I upload/integrate my public key? Certainly, if it was supported as such. That being said, KB functions just fine without an explicit PGP private key, since each device I install KB on generates its own signing key -- that's good enough for KB to verify my social idents and support initial communication; the more proofs they add the better. But more serious and nested "secure" communication would be wiser done elsewhere.
- tialaramex 8y ago
  > Would I upload/integrate my public key? I presume this is a typo, but if so it's a grave one. The naming is very transparent, the intent is that we can give everybody our public keys, they're public, while our private key must remain secret. (I like to use the U2 Lyric "A secret is something you tell one other person, so I'm telling you" to keep straight the difference between secret keys, which we must share with somebody else, and private keys, which we shouldn't share with anybody, although DH means in practice you may never need to explicitly "tell" anyone the secret keys in hybrid systems) [Edited because I made the same dumb typo]
FabHK 8y ago
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-private-key-sharing/ https://blog.filippo.io/on-keybase-dot-io-and-encrypted-priv...
- jwilk 8y ago
  Security strength of RSA is much lower than the key size. 2048-bit RSA gives you only ~112 bits of security.
  - FabHK 8y ago
    That's very informative, thanks. So indeed, with a good passphrase the drop in security is minimal.
- danenania 8y 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.
- Leace 8y 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?

by Leace 8y ago

oedmarap 8y ago

I second this. Would I upload/integrate my public key? Certainly, if it was supported as such. That being said, KB functions just fine without an explicit PGP private key, since each device I install KB on generates its own signing key -- that's good enough for KB to verify my social idents and support initial communication; the more proofs they add the better. But more serious and nested "secure" communication would be wiser done elsewhere.

tialaramex 8y ago
> Would I upload/integrate my public key? I presume this is a typo, but if so it's a grave one. The naming is very transparent, the intent is that we can give everybody our public keys, they're public, while our private key must remain secret. (I like to use the U2 Lyric "A secret is something you tell one other person, so I'm telling you" to keep straight the difference between secret keys, which we must share with somebody else, and private keys, which we shouldn't share with anybody, although DH means in practice you may never need to explicitly "tell" anyone the secret keys in hybrid systems) [Edited because I made the same dumb typo]

FabHK 8y ago

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-private-key-sharing/ https://blog.filippo.io/on-keybase-dot-io-and-encrypted-priv...

jwilk 8y ago
Security strength of RSA is much lower than the key size. 2048-bit RSA gives you only ~112 bits of security.
- FabHK 8y ago
  That's very informative, thanks. So indeed, with a good passphrase the drop in security is minimal.
danenania 8y 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.
Leace 8y 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?