The Microsoft Excel File Format - OpenOffice.org

5.43 FILEPASS
Record FILEPASS, BIFF8, for BIFF8 strong encryption (available only in Excel 10.0 (Excel XP) and later):
Offset Size Contents
0 2 0001 H = BIFF8 standard encryption or strong encryption
2 2 not used, should be equal to next field (0002 H )
4 2 0002 H = BIFF8 strong encryption
6 4 Option flags:
Bit Mask Contents
2 00000004 H Always 1 2
3 00000008 H 1 = Do not encrypt document properties
10 var. FILEPASS Info Block (see below)
var. 4 Size of unique document identifier (uidl)
var. uidl Unique document identifier used to initialise the encryption algorithm
var. uidl Encrypted document identifier used to verify the entered password
var. 4 Size of following verification digest (dl)
var. dl Digest used to verify the entered password
FILEPASS Info Block, BIFF8, for BIFF8 strong encryption:
Offset Size Contents
0 4 Size of the following data in this block, without this field
4 4 Repeated option flags from main record (see above)
8 4 Not used
12 4 Stream encryption algorithm identifier:
00006801 H = RC4 (Ron's Code 4)
00006802 H = SEAL (Secure Encryption Algorithm)
16 4 Password hashing algorithm identifier:
20 4 Hash key length (bits)
00008001 H = MD2 (Message Digest 2)
00008002 H = MD4 (Message Digest 4)
00008003 H = MD5 (Message Digest 5)
00008004 H = SHA-1 (Secure Hash Algorithm)
24 4 Cryptographic provider type:
28 8 Not used
00000001 H = RSA
0000000C H = RSA SChannel
0000000D H = DSS and Diffie-Hellman
00000012 H = DH SChannel
00000018 H = RSA and AES
36 var. Cryptographic provider name, Unicode character array with trailing null character
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