[openssl-dev] OpenSSL and certain PEM formats

[Sean Leonard]

On 12/18/2014 4:41 AM, Salz, Rich wrote:
> Are you trying to be proscriptive (say what people should use) or descriptive (document what is in use)?
>
> Yes, PKCS8-based PRIVATE KEY is better.  But RSA PRIVATE KEY is in (wide) use and should be described.

I am trying to be proscriptively descriptive about what is in use and 
will lead to (continued) interoperability.

In the case of the * PRIVATE KEY labels, not a lot of crypto software 
supports it. The two biggest ones that I know of are OpenSSL and 
PolarSSL. (To my knowledge PolarSSL only supports "RSA PRIVATE KEY" and 
"EC PRIVATE KEY"--all others need to be in "PRIVATE KEY" PKCS #8 
format.) These two OSS implementations may in fact "dominate" the market 
but only a certain market segment (namely web servers, and by extension, 
the web interfaces to web servers by web hosting companies). If you want 
to import a private key into Mac OS X, Mozilla NSS, Microsoft CryptoAPI, 
or the Java VM, you need to package it up (typically with a certificate) 
in a PKCS #12 file.

PKCS #1 is an IETF (adopted) standard but PKCS #1 doesn't prescribe the 
"RSA PRIVATE KEY" label; it only defines the ASN.1 (BER/DER) 
representation. And PKCS #1 is no more or less a standard than the other 
IETF documents for the other key types, like Diffie-Hellman, ECC, etc.

Anyway, the document was approved so it should be published with *minor* 
changes as an RFC soon. I am loathe to add new labels/formats; I am not 
convinced the threshold is met here.

Cheers,

Sean