[FFmpeg-soc] [soc]: r532 - matroska/matroskaenc.c

[David Conrad]

On Jul 25, 2007, at 8:48 PM, Michael Niedermayer wrote:

> Hi
>
> On Thu, Jul 26, 2007 at 02:05:33AM +0200, conrad wrote:
>> Author: conrad
>> Date: Thu Jul 26 02:05:32 2007
>> New Revision: 532
>>
>> Log:
>> Write segment UID
> [...]
>> @@ -507,6 +510,9 @@ static int mkv_write_header(AVFormatCont
>>      MatroskaMuxContext *mkv = s->priv_data;
>>      ByteIOContext *pb = &s->pb;
>>      offset_t ebml_header, segment_info;
>> +    int i;
>> +
>> +    av_init_random(av_gettime(), &mkv->rand_state);
>
> leaks current time (=security risk ...)

What would be best way to seed the random number generator? All the  
other uses of av_init_random() use a constant, but the purpose of the  
segment UID is to be unique among segments, so that other files can  
refer to it. Another idea might be to use a SHA-1 hash of the frame  
contents, but that seems like it would slow down muxing a fair bit.

-David