diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/MANPAGE.md | 5 | ||||
| -rw-r--r-- | Documentation/SECURITY.md | 2 | ||||
| -rw-r--r-- | Documentation/file-format.md | 32 |
3 files changed, 38 insertions, 1 deletions
diff --git a/Documentation/MANPAGE.md b/Documentation/MANPAGE.md index 446ce37..2e440b2 100644 --- a/Documentation/MANPAGE.md +++ b/Documentation/MANPAGE.md @@ -57,6 +57,11 @@ to mount the gocryptfs filesytem without user interaction. **-fusedebug** : Enable fuse library debug output +**-gcmiv128** +: Use an 128-bit IV for GCM encryption instead of Go's default of +96 bits (default true). This pushes back the birthday bound for IV +collisions far enough to make it irrelevant. + **-init** : Initialize encrypted directory diff --git a/Documentation/SECURITY.md b/Documentation/SECURITY.md index dff2fab..a49994a 100644 --- a/Documentation/SECURITY.md +++ b/Documentation/SECURITY.md @@ -18,7 +18,7 @@ File Contents All file contents are encrypted using AES-256-GCM (Galois/Counter Mode). Files are segmented into 4KB blocks. Each block gets a fresh random -96 bit IV each time it is modified. A 128-bit authentication tag (GHASH) +128 bit IV each time it is modified. A 128-bit authentication tag (GHASH) protects each block from modifications. Each file has a header containing a random 128-bit file ID. The 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 |