Implementing-cryptography-using-python

52 Chapter 2 ■ Cryptographic Protocols and Perfect Secrecy
Table 2.2: Bitwise Operators
OPERATOR DESCRIPTION EXAMPLE
& (Binary AND)
Operator copies a bit to the result if it
exists in both operands.
| (Binary OR) Operator copies a bit if it exists in either
operand.
^ (Binary XOR)
~ (Binary Ones
Complement)
<< (Binary Left
Shift)
>> (Binary Right
Shift)
Operator copies the bit if it is set in one
operand but not both.
Operator is unary and has the effect of
“flipping” bits.
The left operand’s value is moved left
by the number of bits specified by the
right operand.
The left operand’s value is moved right
by the number of bits specified by the
right operand.
(a & b) (means 0000
1100)
(a | b) = 61 (means
0011 1101)
(a ^ b) = 49 (means
0011 0001)
(~a ) = -61 (means
1100 0011 in 2’s
complement form due to a
signed binary number)
a << 2 = 240 (means
1111 0000)
a >> 2 = 15 (means
0000 1111)
The bin() function in Python can be used to convert our integers 60 and 13
to their binary format. Type the following into the Python shell:
>>> a = 60
>>> b = 13
>>> print (bin(a))
0b111100
>>> print (bin(b))
0b1101
>>> print (bin(a &amp; b))
0b1100
>>> print (bin(a | b))
0b111101
>>> print (bin(a ^ b))
0b110001
>>> print (bin(~a))
-0b111101
>>> print (bin(a<<2))
0b11110000
>>> print (bin(a>>2))
0b1111
Each value maps as shown. Alphanumeric characters, such as A, B, C, can
also be converted to a binary format. The use of the ordinal function, ord(),
will give a numerical value to an ASCII letter. Examine the following example: