Cryptography Reference
In-Depth Information
SET is presented via its components, the first being vital and innovative.
SET Dual Signature Protocol
Background Assumptions
: This concept of “dual signatures” is new to
the DSS arena. Dual signatures permit two data blocks to be intimately linked,
yet sent to two different entities for handling. Two mechanisms allowing this to
occur within SET are the following.
1. The
order information
(OI) message (which contains order reference gener-
ated in the exchange between Alice and Bob in her shopping phase before
the first SET message is sent, which we will detail below, but contains no
explicit order information such as the cost of Alice's chosen items). The
OI is sent to Bobfor processing.
2. At the same time, a
payment information
(PI) message is sent to Trent
who requires it (typically for authorization with the issuer and acquirer).
Protocol Steps
:
1. Given a public cryptographic hash function
H
, a message digest (see
page 170) is created for the OI, called the
OI message digest
H
(
OI
)=
(
OIMD
); and for the PI, called the
PI message digest
H
(
PI
)=(
PIMD
).
2. The OIMD and PIMD are concatenated to produce a new data block
C
=
(
OIMD, PIMD
).
3.
C
is hashed to produce a new data block
H
(
C
), called the
payment order
message digest
denoted by (
POMD
).
4. The POMD is encrypted using the signer's private key to produce a (dual)
digital signature.
In the following diagram,
k
is the signer's private key,
DS
is the dual signa-
ture, and all other acronyms are as given in the above protocol description.
Diagram 6.2 (SET Dual Signature Illustrated)
✄
✂
✁
✄
✂
✁
✄
✂
✁
PI
→
H
→
PIMD
✞
✝
✆
✄
✂
✁
✄
✂
✁
✄
✂
✁
✄
✂
✁
(
OIMD, PIMD
)
→
H
→
POMD
→
k
→
DS
✄
✂
✁
✄
✂
✁
✄
✂
✁
OI
→
H
→
OIMD
Now we describe the components of the SET scheme, which will employ the
dual signature protocol for security. Later we will discuss the details of how the
security needs are met by the use of dual signature to provide confidentiality,
integrity, and authentication. We begin with the first stage in Diagram 6.2,
initiated by Alice, who wants to do business with Bob over the Internet.
Search WWH ::
Custom Search