Terms & Definitions
SHA1 cryptographic hash
The SHA1 cryptographic hash is a
NIST Secure
Hash Standard function.
Some of the most important properties of cryptographic / secure hash are:
 Hash inversion is hard:
For any x:
given only hash(x), it is hard to find x
This property assumes that the value x is not known.
It also assumes that x is not more
than the maximum value that can be hashed.
 Hash forgery is hard:
Given x, it is hard to find a
y != x
such that hash(y) = hash(x)
This property assumes that x and
y are not more
than the maximum value that can be hashed.
 Linear hash operations are hard:
For any x:
given only hash(x), and c != 0,
it is hard to compute hash(x + c)
This property assumes that the value x is not known.
It also assumes that both x + c and
x are not more than the maximum value that can be hashed.
