Implementing-cryptography-using-python

Chapter 6 ■ Using Cryptography with Images 183
The resulting image will look like Figure 6.8.
Figure 6.8: ECB encrypted plane
Now we will reverse the process. The decryption process will look like the
following:
with open("plane_ecb.bmp", "rb") as f:
byteblock = f.read()
byteblock_trimmed = byteblock[64:-6]
plaintext = cipher.decrypt(byteblock_trimmed)
plaintext = byteblock[0:64] + plaintext + byteblock[-6:]
with open("dplane_ecb.bmp", "wb") as f:
byteblock = f.write(plaintext)
The result, shown in Figure 6.9, will produce a decrypted version that matches
the original version.
Figure 6.9: ECB decrypted plane
Depending on the image you choose, you will have a variable of bytes that
will need to be captured. The following code stores the value in a pad variable.
To simplify the code, I multiplied it by −1 to produce a negative number. The