DES question, anyone can help?# Security - 系统安全
c*x
1 楼
This is an interesting problem, I still can’t figure it out:
If in a meet-in-the-middle known plaintext attack, I have known the (P1, C1)
and (P2,C2), and
C1=DESK2(DESK1(P1))
C2=DESK2(DESK1(P2))
To find out the K1, K2, I store and sort two tables:
Table1 stores the pairs of (DESK(P1), K), K is from 0 to 256-1, sort by the
first item
Table2 stores the pairs of (DES-1K’(C1), K’), K’ is from 0 to 256-1, sort
by the first item
The question is, how many pairs(K, K’) with the same first field respec
If in a meet-in-the-middle known plaintext attack, I have known the (P1, C1)
and (P2,C2), and
C1=DESK2(DESK1(P1))
C2=DESK2(DESK1(P2))
To find out the K1, K2, I store and sort two tables:
Table1 stores the pairs of (DESK(P1), K), K is from 0 to 256-1, sort by the
first item
Table2 stores the pairs of (DES-1K’(C1), K’), K’ is from 0 to 256-1, sort
by the first item
The question is, how many pairs(K, K’) with the same first field respec