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Update signing.md

matthew/js-fixes
Richard van der Hoff 2019-11-08 13:48:34 +00:00
parent 52098b3af7
commit a9c7bde457
1 changed files with 7 additions and 5 deletions
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docs/signing.md
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@ -49,13 +49,14 @@ compromised keys, and sends a pre-key message using a shared secret $`S`$,
where:
```math
S = ECDH\left(I_A,\,E_E\right)\;\parallel\;ECDH\left(E_A,\,I_B\right)\;
\parallel\;ECDH\left(E_A,\,E_E\right)
S = ECDH\left(I_A,E_E\right)\;\parallel\;
ECDH\left(E_A,I_B\right)\;\parallel\;
ECDH\left(E_A,E_E\right)
```
Eve cannot decrypt the message because she does not have the private parts of
either $`E_A`$ nor $`I_B`$, so cannot calculate
$`ECDH\left(E_A,\,I_B\right)`$. However, suppose she later compromises
$`ECDH\left(E_A,I_B\right)`$. However, suppose she later compromises
Bob's identity key $`I_B`$. This would give her the ability to decrypt any
pre-key messages sent to Bob using the compromised one-time keys, and is thus a
problematic loss of forward secrecy. If Bob signs his keys with his Ed25519
@ -66,8 +67,9 @@ On the other hand, signing the one-time keys leads to a reduction in
deniability. Recall that the shared secret is calculated as follows:
```math
S = ECDH\left(I_A,\,E_B\right)\;\parallel\;ECDH\left(E_A,\,I_B\right)\;
\parallel\;ECDH\left(E_A,\,E_B\right)
S = ECDH\left(I_A,E_B\right)\;\parallel\;
ECDH\left(E_A,I_B\right)\;\parallel\;
ECDH\left(E_A,E_B\right)
```
If keys are unsigned, a forger can make up values of $`E_A`$ and