RADIUS attribute from rfc5090
If this attribute is present in an Access-Request message, a
RADIUS server implementing this specification MUST treat the
Access-Request as a request for Digest Authentication. When a
RADIUS client receives a (Proxy-)Authorization header, it puts
the request-digest value into a Digest-Response Attribute.
This attribute (which enables the user to prove possession of
the password) MUST only be used in Access-Request packets.Type
103 for Digest-Response.
When using HTTP Digest, the text field is 32 octets long and
contains a hexadecimal representation of a 16-octet digest
value as it was calculated by the authenticated client. Other
digest algorithms MAY define different digest lengths. The
text field MUST be copied from request-digest of digest-
response without surrounding quotes.