**3.2 AES decryption**

A cipher text of 128-bits is processed through 10 inverse rounds. Each round contains processes like inverse byte substitution, inverse shift rows, inverse mix columns, and add round key.

**Figure 17** shows implementation of inverse round function.

Inverse round function consists of inverse s-box, inverse shift row, and inverse mix column as shown in **Figure 18**.

**Figure 19** shows implementation of inverse mix column.

Inverse mix column consists of four groups, i.e., group\_1, group\_2, group\_3, and group\_4. **Figure 20** shows implementation of group. Each group consists of multiplication blocks like mul\_blk, mul\_blk1, mul\_blk2, and mul\_blk3. **Figure 21** shows implementation of multiplication block.

Each multiplication block consists of three multipliers mul\_2, mul\_4, and mul\_8 and EX-OR operations. **Figure 22** shows implementation of multipliers.

**Figure 12.** *Implementation of s-box.*

**Figure 23** shows implementation of inverse shift row. **Figure 24** shows implementation of inverse s-box.

### **3.3 Tools utilized**
