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Update docs

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This commit is contained in:
Alexey Avramov
2025-08-25 21:39:05 +09:00
parent be76d1ac34
commit b9c6971435
1 changed files with 6 additions and 3 deletions
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9
docs/SPECIFICATION.md
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@@ -65,6 +65,7 @@ Payload consists of Comments up to 512 bytes and File contents from 0 bytes.
- The final byte string is **truncated** to a fixed size of `PROCESSED_COMMENTS_SIZE = 512` bytes. If the original comment (after UTF-8 encoding) is longer than 512 bytes, it will be truncated.
```
raw_comments_bytes = encode_utf8(user_comment)
processed_comments = (raw_comments_bytes || 0xFF || read(CSPRNG, PROCESSED_COMMENTS_SIZE))[:PROCESSED_COMMENTS_SIZE]
```
- If no comment is provided, `processed_comments` are generated in a special way (see `get_processed_comments` code) to minimize the chance of accidentally matching a valid comment structure, if the "fake MAC" option is *not* used. If "fake MAC" is used, `processed_comments` are simply filled with random bytes `read(CSPRNG, PROCESSED_COMMENTS_SIZE)`.
@@ -146,6 +147,7 @@ Two 16-byte salts are used in the process:
```
argon2_salt = read(CSPRNG, 16)
blake2_salt = read(CSPRNG, 16)
```
@@ -153,6 +155,7 @@ blake2_salt = read(CSPRNG, 16)
```
argon2_salt = cryptoblob[0:16]
blake2_salt = cryptoblob[-16:]
```
@@ -166,7 +169,7 @@ There are 5 steps:
2. Sorting IKM digest list, getting sorted IKM digest list.
3. Hashing sorted IKM digest list, getting Argon2 password.
4. Key stretching with Argon2, getting Argon2 tag.
5. Splitting Argon2 tag, getting keys for padding, encryption, and authentication.
5. Deriving keys for padding, encryption, and authentication from Argon2 tag.
### 1. Collecting and handling keyfiles and passphrases, getting IKM digest list
@@ -309,8 +312,8 @@ ciphertext chunk = ChaCha20(plaintext chunk, key = enc_key, nonce++)
**Overview of nonce incrementation process:**
|Counter|nonce|Data to encrypt|
|-|—|-|
|0|-|(initial counter value; not used for encryption)|
|-|-|-|
|0|—|(initial counter value; not used for encryption)|
|1|`0x010000000000000000000000`|Processed comments, size: 512 B|
|2|`0x020000000000000000000000`|File contents chunk 0, size: 16 MiB|
|3|`0x030000000000000000000000`|File contents chunk 1, size: 16 MiB|