> The NamedParameterSpec object holds the name only, and not the key size.
The name is not a meaningless string, it refer to a specific thing. For
more examples, please refer to the standard names documentation, every
name has its specific meaning and the background. If the name is just a
meaningless string, there is nothing we can do for it and we may not
want to define a meaningless API.
The parse of the NamedParameterSpec name is really about the
implementation details. For example, for KeyFactory:
public PublicKey engineGeneratePublic(KeySpec keySpec) {
if (the algorithm is 'x25519') {
// use the X25519 parameters, including key size
} else if ('x448') {
// use the X25519 parameters, including key size
}
}
There are a few alternatice ways. You can define a enum in the XDH
provider, or just use switch, or use Map, or something else you like.
Which one is a better one, it may depends on the implementation details.
Please don't define the x25519 parameters in JSSE. JSSE should use the
'x25519' name (via NamedParameterSpec object) only. The underlying JCE
provider should take the responsibility to support the
NamedParameterSpec and defines the internal/private parameters for the
specific name.
Thanks,
Xuelei
On 9/7/2018 5:49 AM, Adam Petcher wrote:
On 9/6/2018 4:49 PM, Xuelei Fan wrote:
I asked the question in a previous email. The key size for x25529 is
fixed, right?
Right.
If it is not right, stop here and tell me that it is not right. Keep
reading if it is right.
OK, as the key size for x25519 is fixed, when you know the algorithm
is x25519, you know the key size. Does it sound right to you?
Possibly right---it depends on what you mean by "know". If all you have
is the name, then you need use a static mapping to look up the key length.
If it is not right, stop here and tell me that it is not right.
Otherwise, keep reading.
From the name you know the key size, when you create a
NamedParameterSpec object for "x25519", you know the name and key size
from the object, right?
The NamedParameterSpec object holds the name only, and not the key size.
We create the NamedParameterSpec from the algorithm name in the
NamedGroup enum, which also doesn't have the key size. Are you
suggesting that I add the key size to this enum as well? Like this:
// x25519 and x448
X25519 (0x001D, "x25519", true, "x25519", 255,
ProtocolVersion.PROTOCOLS_TO_13),
X448 (0x001E, "x448", true, "x448", 448,
ProtocolVersion.PROTOCOLS_TO_13),
The constructor will take this length and store it. Then we can get this
value out of the NamedGroup in XDHKeyExchange and pass it in to the
methods of ECUtil so we don't need to get it from XECParameters. Is this
what you had in mind?
