MultiCast Discovery

[nncp.git] / doc / eblob.texi

diff --git a/doc/eblob.texi b/doc/eblob.texi
index baaa718907e820411b32e324bb11711b3475c71f..45de886d3defe40b7a82905107f64a79293d02ca 100644 (file)
--- a/doc/eblob.texi
+++ b/doc/eblob.texi
@@ -32,16 +32,16 @@ winner).
 Eblob is an @url{https://tools.ietf.org/html/rfc4506, XDR}-encoded structure:
 
 @verbatim
-+-------+------------------+------------+
-| MAGIC | S | T | P | SALT | BLOB | MAC |
-+-------+------------------+------------+
++-------+------------------+------+
+| MAGIC | S | T | P | SALT | BLOB |
++-------+------------------+------+
 @end verbatim
 
 @multitable @columnfractions 0.2 0.3 0.5
 @headitem @tab XDR type @tab Value
 @item Magic number @tab
     8-byte, fixed length opaque data @tab
-    @verb{|N N C P B 0x00 0x00 0x01|}
+    @verb{|N N C P B 0x00 0x00 0x03|}
 @item S, T, P @tab
     unsigned integer @tab
     Space cost, time cost and parallel jobs number
@@ -50,18 +50,19 @@ Eblob is an @url{https://tools.ietf.org/html/rfc4506, XDR}-encoded structure:
     Randomly generated salt
 @item Blob @tab
     variable length opaque data @tab
-    Encrypted data itself
-@item MAC @tab
-    32 bytes, fixed length opaque data @tab
-    BLAKE2b-256 MAC of encrypted blob
+    Authenticated and Encrypted data itself
 @end multitable
 
-Blob's encryption is done using
-@url{https://www.schneier.com/academic/twofish/, Twofish} algorithm with
-256-bit key in
-@url{https://en.wikipedia.org/wiki/Counter_mode#Counter_.28CTR.29, CTR}
-mode of operation with zero initialization vector.
-@code{balloon(BLAKE2b-256, S, T, P, salt, password)} gives the main key,
-that is fed to @url{https://en.wikipedia.org/wiki/HKDF,
-HKDF}-BLAKE2b-256 KDF. Actual encryption key for Twofish and
-authentication key for MAC are derived from that KDF.
+@enumerate
+@item generate the main key using @code{balloon(BLAKE2b-256, S, T, P,
+salt, password)}
+@item initialize @url{https://blake2.net/, BLAKE2Xb} XOF with generated
+main key and 32-byte output length
+@item feed @verb{|N N C P B 0x00 0x00 0x03|} magic number to XOF
+@item read 32-bytes of blob AEAD encryption key
+@item encrypt and authenticate blob using
+    @url{https://cr.yp.to/chacha.html, ChaCha20}-@url{https://en.wikipedia.org/wiki/Poly1305, Poly1305}.
+    Blob is splitted on 128 KiB blocks. Each block is encrypted with
+    increasing nonce counter. Eblob packet itself, with empty blob
+    field, is fed as an additional authenticated data
+@end enumerate