0x00 prefix for R and S values in DER signature

[luv2drnkbr]

I've noticed that some scriptsigs have a 0x00 prefixing the 32 byte R and S values in the signatures, and some signatures do not have that.  I was hoping somebody knows the reason behind that and can explain to me if and when the prefix is necessary, and why.

[Pieter Wuille]

It's a DER requirement to prefix a 0x00 byte to an encoded integer if the integer otherwise starts with a byte >= 0x80. If not, it would be interpreted as a negative number.

[luv2drnkbr]

Thanks for that clear explanation!