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Correct documentation of PPK key derivation.

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When I transcribed the code into this document, I misread 'put_data'
as 'put_string' in several places, and documented SSH-style string
length headers that do not actually exist in the format.
This commit is contained in:
Simon Tatham 2021-02-20 10:13:49 +00:00
parent eda4ca6e65
commit ce60ca727c
1 changed files with 7 additions and 3 deletions
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10
doc/pubkeyfmt.but
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@ -255,14 +255,18 @@ Each hash in the sequence is a SHA-1 hash of the following data:
\b \cw{uint32}: a sequence number. This is 0 in the first hash, and \b \cw{uint32}: a sequence number. This is 0 in the first hash, and
increments by 1 each time after that. increments by 1 each time after that.
\b \cw{string}: the passphrase. \b the passphrase, without any prefix length field.
The MAC key is also derived from the passphrase. It is a single SHA-1 The MAC key is also derived from the passphrase. It is a single SHA-1
hash of the following data: hash of the following data:
\b \cw{string}: the fixed string \cq{putty-private-key-file-mac-key}. \b the fixed string \cq{putty-private-key-file-mac-key}, without any
prefix length field.
\b \cw{string}: the passphrase. \b the passphrase, without any prefix length field. (If the key file
is unencrypted, the MAC is still computed in the same way, and the
passphrase is taken to be the empty string for the purpose of deriving
the MAC key.)
\H{ppk-v1} PPK version 1 \H{ppk-v1} PPK version 1