Rockbox Development > New Ports

Creative Zen Vision:M

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aliask:

--- Quote from: mcuelenaere on April 04, 2007, 12:10:56 PM ---Hi,

* The last block (the NULL block) is 20 chars long, and contains a hash/checksum. It's no common used one, cause MD4, MD5, SHA1 don't match it. (20 chars should mean 160-bit)
--- End quote ---

SHA1 is 160 bit.

mcuelenaere:

--- Quote from: aliask on April 04, 2007, 11:16:52 PM ---SHA1 is 160 bit.

--- End quote ---

Indeed, but they don't match:

SHA-1 OF 'FFIC' BLOCK: 9A 4F 20 B0 2B F3 91 99 D7 A6 6A FD C7 A6 1C 68 10 AF 82 4A

DATA OF 'NULL' BLOCK: 41 A3 63 2B 2E C2 C6 F7 DF 31 99 D8 61 2E 76 99 77 07 CB 19

BTW, this is the 010 Editor Template I use for parsing the blocks, it works perfectly.

--- Code: ---//--------------------------------------
//--- 010 Editor v2.0 Binary Template
//
// File: Creative firmware (nk.bin)-Parser
// Author: l_e
// Revision: 0.1
//--------------------------------------

typedef struct {
CHAR BlockID[4];
DWORD Size;
if (BlockID == "FNIC"){
UCHAR Desc[96];
} else if (BlockID == "LLUN" || BlockID == "FFIC"){
UCHAR Data[ Size ];
} else {
UCHAR Desc[32];
UCHAR Data[ Size - sizeof(Desc) ];
}
} BLOCK;
//--------------------------------------------

CHAR[] StrRev( CHAR s[] )
{
local int sz;
local int up;
local CHAR strng[sizeof(s)];

for (sz =sizeof(s)-1,up=0;up

iSE:
I'm no expert on cryptography, but supposed we were to literally try to brute force that encryption, how long would that take? If its a reasonable time frame, say a few months I have an incredibly fast computer not doing anything at the moment.

larryzotter:
But how would u 'verify' that the bruteforced checksum is correct? Try and update the firmware with the checksum to the ZVM and see if it accepts it? That would take a looooooong time...

Bagder:

--- Quote from: iSE on April 05, 2007, 10:06:31 AM ---I'm no expert on cryptography, but supposed we were to literally try to brute force that encryption,

--- End quote ---

160 bits SHA1 is simply not possible to brute-force within our lifetimes, even if we'd use a hundred thousand modern PCs. Compare with the 72bit RC5 cracking contest.

Edit: contest is not contents ;-)

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