DES S-box Lookup

Reference for DES Feistel Round

Input: 6 bits b₁ b₂ b₃ b₄ b₅ b₆
Row = b₁ b₆ (2 bits → 0..3)
Column = b₂ b₃ b₄ b₅ (4 bits → 0..15)
Output: 4 bits from S-box[row][col]
b₁ b₂ b₃ b₄ b₅ b₆ ROW COLUMN ROW

Example: 011000 into S1

Eight 6-bit chunks feed S1 through S8 in order. Concatenate eight 4-bit outputs → 32-bit f-function result → P-permutation.

DES Illustrated PDF · Stallings Ch.3