Security - Telenor

Before continuing, A must examine M to see if it
constitutes an acceptance or refusal on B 1 ’s part.
If it is a refusal, the protocol is finished. If it is
an acceptance, the protocol continues for the initial
platform as follows:
3. A m3
→ B1 :
As(A, B1,iA,B1p(KA))
m4
4. B1 → A :
B1s(B1,A,iA,H(m3))
The contents of the messages is given in Table 2.
When all necessary verifications have been
done, B1 can begin executing the agent. This
execution continues until the agent requests
migration to a new platform B2 . The migration
from any given Bi to Bj requires a separate protocol.
Denote by T p
B the trace produced by the part
i
of the execution carried out on Bi . The migration
to the next platform Bj is initiated by the following
three messages:
1.
m
2. Bi
′
→ Bj :
Bis(KBi(p, SBi),H(m))
3.
m
Bi → Bj :
Bis(Bi,Bj, agentA,H(T p
Bi ),H(SBi,tBi))
m
Bj
′′
→ Bi :
Bjs(Bj,Bi,iA,H(m, m ′ ),M)
The last field in the third message (M) contains
either B j ’s acceptance to run the agent, or its
refusal to run the agent. The contents of the
messages are given in Table 3.
7 Authenticity
There are two types of authenticity:
1. authenticity of origin; and
2. authenticity of identity.
Authenticity of origin deals with proving or disproving
the claimed identity of the creator of
some data, be it art, code or something else.
Authenticity of origin is a very hard problem,
which might not have any good solution. With
respect to agents, the most relevant cases probably
include authenticity of the origin of:
1. data carried by an agent from its sender;
2. data acquired by an agent at some platform;
3. an agent’s code.
Telektronikk 3.2000
Message Sender Recipient Message part Explanation
m1 A B1 As ( Signature generated by A
A, A’s identity
B1 , B1 ’s identity
EKA ( Encryption with A’s key KA p, The agent’s code
SA ), The agent’s initial state
As ( Signature generated by A
A, A’s identity
iA , The agent’s identifier
tA , Time stamp for agent dispatch
H(p), Hash of agent’s code
T)) Identity of TTP
m2 B1 A B1s ( Signature generated by B1 B1 , B1 ’s identity
A, A’s identity
iA , The agent’s identifier
H(m1 ), Hash of previous message
M) B1 ’s reply
It is important to note that authenticity of origin
is not the same as authenticity of the sender: data
may be sent without their creator having to do
the sending in person.
Authenticity of identity deals in general with
proving or disproving the identity claimed by
a subject. Traditionally, authenticity has been
proven using one or more independent techniques,
and efforts have been concentrated on
the case where humans prove their identity to an
(automated) subject of some sort, or where automated
subjects need to prove their identities to
each other as the initial step in some protocol.
Within automated environments, only passive
data have been authenticated. What one effectively
needs for agents is authentication of process
instances.
Message Sender Recipient Message part Explanation
Table 1 Initialization of protocol
for execution traces
Table 2 The rest of the initialization
of the protocol for execution
traces, if B 1 agrees to
participate in the protocol
m3 A B1 As ( Signature generated by A
A, A’s identity
B1 , B1 ’s identity
iA , The agent’s identifier
B1p ( Encryption with B1 ’s public key
KA )) A’s symmetric encryption key
m4 B1 A B1s ( Signature generated by B1 A A’s identity
iA , The agent’s identifier
H(m3 )) Hash of message m3 43