Explain cryptography hash function criteria and compare MD-5 and SHA-1.

254views

written 8.3 years ago by

• modified 8.3 years ago

Cryptographic Hash Function

Cryptographic hash function takes a message of arbitrary length and creates a message digest of fixed length.
The cryptographic hash function h(x) criteria are as follows:

Compression: For any size of input x, the output length of y = h(x) is small. Hash functions produce a fixed size output regardless of the length of the input.

Efficiency: It must be easy to compute h(x) for any input x. the computational effort required to compute h(x) will certainly grow with the length of x, but it should not grow too fast.

One-way: Given any value y, it is computationally infeasible to find a value x such that $h(x) = y.$ It is difficult to invert the hash.

Weak collision resistance: Given x and h(x) it is infeasible to find y with $y ≠ x$ such that $h(y) = h (x).$

Strong collision resistance: It is infeasible to find y with $x ≠ y$ such that $h(x) = h(y)$.

Comparison between MD-5 and SHA-1:

Parameters	MD-5	SHA-1
Message digest size	Message digest 128 bits	Message digest is 160 bit long.
Speed	Faster because of size	Slower compared to MD-5
Brutte force attack possibility	Brute force attack is of the order $2^{128}$	Brute force attack is of the order $2^{160}$
Collision	Difficulty in producing same digest is $2^{64}$	Difficulty in producing same message is $2^{80}$
Secure	Less secure	More secure
Cryptanalytic attack	Vulnerable to cryptanalysis attack	Non-vulnerable to cryptanalytic attack
Buffers used	Four buffers of 32 bits each	Five buffers of 32 bits
Format	No format used	Big endian format used to store values

ADD COMMENT EDIT