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On 7/4/2018 7:22 PM, Kristian Fiskerstrand wrote: |
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> On 07/05/2018 01:07 AM, Joshua Kinard wrote: |
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>>> @@ -64,6 +66,8 @@ not be used to commit. |
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>>> |
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>>> b. RSA, >=2048 bits (OpenPGP v4 key format or later only) |
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>>> |
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>>> + c. ECC, curve 25519 |
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>>> + |
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>>> 3. Key expiry: 5 years maximum |
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>>> |
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>>> 4. Upload your key to the SKS keyserver rotation before usage! |
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>>> |
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>> Add a minimum key size here for ECC. They have different bit sizes than |
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>> classic DSA/RSA keys. A quick read indicates that a 224-bit ECC key is roughly |
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>> equivalent to a 112-bit symmetric key, which is what a 2048-bit RSA key is |
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>> equivalent to, so the logical minimum for ECC looks like 'nistp256'. The |
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>> maximum is 521-bits on ECC (nistp521). |
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>> |
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>> Also move the mention of Ed25519 keys to their own bullet and clarify that they |
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>> don't allow for a key length, as I think that's hardcoded in some capacity. |
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> |
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> following the comma-style of the rest of the document, the ECC part |
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> should likely be read as curve25519 being the only acceptable curve, |
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> which is 256 bits (roughtly 128 bit shannon entropy equivalent) |
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> |
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> that said, I'm not aware of any curves defined with a lower security |
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> margin than this for OpenPGP in general. The known curves in the |
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> ecosystem are |
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> |
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> let oid_to_psize oid = |
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> let psize = match oid with |
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> | "\x2b\x81\x04\x00\x23" -> 521 (* nistp521 *) |
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> | "\x2b\x81\x04\x00\x22" -> 384 (* nistp384 *) |
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> | "\x2a\x86\x48\xce\x3d\x03\x01\x07" -> 256 (* nistp256 *) |
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> | "\x2b\x24\x03\x03\x02\x08\x01\x01\x07" -> 256 (* brainpoolP256r1 *) |
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> | "\x2b\x24\x03\x03\x02\x08\x01\x01\x0b" -> 384 (* brainpoolP384r1 *) |
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> | "\x2b\x24\x03\x03\x02\x08\x01\x01\x0d" -> 512 (* brainpoolP512r1 *) |
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> | "\x2b\x81\x04\x00\x0a" -> 256 (* secp256k1 *) |
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> | "\x2b\x06\x01\x04\x01\xda\x47\x0f\x01" -> 256 (* Ed25519 *) |
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> | _ -> failwith "Unknown OID" |
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> |
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|
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By "only acceptable curve", do you mean we shouldn't allow the nistp* key |
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types, only Ed25519? |
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|
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-- |
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Joshua Kinard |
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Gentoo/MIPS |
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kumba@g.o |
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rsa6144/5C63F4E3F5C6C943 2015-04-27 |
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177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943 |
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"The past tempts us, the present confuses us, the future frightens us. And our |
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lives slip away, moment by moment, lost in that vast, terrible in-between." |
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--Emperor Turhan, Centauri Republic |
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