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Add encrypted file layout table in README

This commit is contained in:
Matéo Duparc 2021-08-31 12:23:25 +02:00
parent 882a917971
commit f6fe3912c6
Signed by: hardcoresushi
GPG Key ID: 007F84120107191E
1 changed files with 36 additions and 0 deletions
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README.md
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@ -154,6 +154,7 @@ let hmac = Hmac::new(
blake2b, //hash function
);
hmac.update(random_salt);
//integers are encoded in big-endian
hmac.update(argon2_time_cost);
hmac.update(argon2_memory_cost);
hmac.update(argon2_parallelism);
@ -182,6 +183,41 @@ Once the whole plaintext is encrypted, doby computes and appends the HMAC to the
output.write(hmac.digest());
```
So here is what an encrypted file layout looks like:
<table>
<tr>
<th align="left">Magic bytes</th>
<td>4 bytes</td>
</tr>
<tr>
<th align="left">Salt</th>
<td>64 bytes</td>
</tr>
<tr>
<th align="left" rowspan="3">Argon2 parameters</th>
<td>Time cost: 4 bytes</td>
</tr>
<tr>
<td>Memory cost: 4 bytes</td>
</tr>
<tr>
<td>Parallelism cost: 1 byte</td>
</tr>
<tr>
<th align="left">Encryption cipher</th>
<td>1 byte</td>
</tr>
<tr>
<th align="left">Ciphertext</th>
<td>Exact same size as the plaintext</td>
</tr>
<tr>
<th align="left">HMAC</th>
<td>64 bytes</td>
</tr>
</table>
### Decryption
doby reads the public encryption values from the input header to get all parameters needed to re-derive the `master_key` from the password with Argon2.