From 1caa9258685fa5fad8935d3bfcd0eac7d7f84f1e Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher
Date: Sat, 19 Dec 2015 14:41:39 +0100
Subject: Increase GCM IV size from 96 to 128 bits

This pushes back the birthday bound for collisions to make it virtually
irrelevant.
---
 Documentation/file-format.md | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 Documentation/file-format.md

(limited to 'Documentation/file-format.md')

diff --git a/Documentation/file-format.md b/Documentation/file-format.md
new file mode 100644
index 0000000..b0d4b55
--- /dev/null
+++ b/Documentation/file-format.md
@@ -0,0 +1,32 @@
+File Format
+===========
+
+Header
+
+	 2 bytes header version (big endian uint16, currently 2)
+	16 bytes file id
+
+Data block
+
+	16 bytes GCM IV (nonce)
+	1-4096 bytes encrypted data
+	16 bytes GHASH
+
+
+Example: 1-byte file
+--------------------
+
+	Header     18 bytes
+	Data block 33 bytes
+
+Total: 51 bytes
+
+
+Example: 5000-byte file
+-----------------------
+
+	Header       18 bytes
+	Data block 4128 bytes
+	Data block  936 bytes
+
+Total: 5082 bytes
-- 
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