Nothing really they are both binary PCKS7 files the (.p7 .p7a .p7b .p7c) refers to the method used to encode the file if the extension is p7 then the decoder has to decide which method to use to decode it. If it is another variation it uses that method to decode it.
The most common is by far .p7b almost to the exclusion of every other, if you change the file extension on a .p7 file to .p7b you should be able to open it in windows. This is the easy way to get a cvc for a particular firmware image.
Nothing really they are both binary PCKS7 files the (.p7 .p7a .p7b .p7c) refers to the method used to encode the file if the extension is p7 then the decoder has to decide which method to use to decode it. If it is another variation it uses that method to decode it.
The most common is by far .p7b almost to the exclusion of every other, if you change the file extension on a .p7 file to .p7b you should be able to open it in windows. This is the easy way to get a cvc for a particular firmware image.