On Sun, 2005-07-17 at 12:03 -0400, Jorey Bump wrote:
> What is the maximum length (if string) or size (if number) of a serial 
> number?
> 
> I am using the current datetime to set the initial serial number for my 
> CA to provide a reasonable measure of uniqueness:
> 
>   # example: 200507171152001
>   SERIALINIT=$(date +%Y%m%d%H%M)001
>   echo $SERIALINIT > serial
> 
> Do I need to be concerned with the number of characters or the number of 
> bits used to represent the serial number? Is there an RFC that defines this?
> 

I found this in RFC 2459 (http://www.faqs.org/rfcs/rfc2459.html)

*******************************************************************
4.1  Basic Certificate Fields

   The X.509 v3 certificate basic syntax is as follows.  For signature
   calculation, the certificate is encoded using the ASN.1 distinguished
   encoding rules (DER) [X.208].  ASN.1 DER encoding is a tag, length,
   value encoding system for each element.

          ...

   CertificateSerialNumber  ::=  INTEGER
 
          ...
*******************************************************************

and then I found this (http://gost.isi.edu/brian/security/asn1.html)

********************************************************************
         ...

And that's all that we need. This second specification introduces us to another 
primitive, INTEGER, which is exactly what it sounds like, an integer. The 
difference between this integer and that which resides on most machines is that 
this one is arbitrarily large: the ASN.1 encoding for integer allows for 
integers 
of whatever size.
         ...
********************************************************************

Here is the ASN.1 website - http://asn1.elibel.tm.fr/

Todd

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