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"""
Key handling utilities for Diffie-Hellman keys.
"""
from asn1crypto.algos import DHParameters
from asn1crypto.core import Integer
from . import biginteger
from ..constants import Attribute
from ..exceptions import AttributeTypeInvalid
def decode_dh_domain_parameters(der):
"""
Decode DER-encoded Diffie-Hellman domain parameters.
:param bytes der: DER-encoded parameters
:rtype: dict(Attribute,*)
"""
params = DHParameters.load(der)
return {
Attribute.BASE: biginteger(params['g']),
Attribute.PRIME: biginteger(params['p']),
}
def encode_dh_domain_parameters(obj):
"""
Encode DH domain parameters into DER-encoded format.
Calculates the subprime if it isn't available.
:param DomainParameters obj: domain parameters
:rtype: bytes
"""
asn1 = DHParameters({
'g': int.from_bytes(obj[Attribute.BASE], byteorder='big'),
'p': int.from_bytes(obj[Attribute.PRIME], byteorder='big'),
})
return asn1.dump()
def encode_dh_public_key(key):
"""
Encode DH public key into RFC 3279 DER-encoded format.
:param PublicKey key: public key
:rtype: bytes
"""
asn1 = Integer(int.from_bytes(key[Attribute.VALUE], byteorder='big'))
return asn1.dump()
def decode_dh_public_key(der):
"""
Decode a DH public key from RFC 3279 DER-encoded format.
Returns a `biginteger` encoded as bytes.
:param bytes der: DER-encoded public key
:rtype: bytes
"""
asn1 = Integer.load(der)
return biginteger(asn1)
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