Hash functions in cryptography takes a message of arbitary length and creates a message digest of fix length. Moreover, we have already seen about cryptography, let us know about hash functions.
Firstly, a hash function H accepts a variable length block of data M as input and produces a fix size hash value h= H(M). Secondly, a good hash function has the property that any change in a single bit with high probability result in change to the hash code.
Applications of Hash functions
- Message authentication
- Digital Signature
- One way password file
Firstly, message authentication provides secure transfer of each and every message between employees. MAC takes a secret key as an input and produces a hash value.
Moreover, digital signature is used to validate integrity and authenticity of a message. In digital signature, hash value of a message is encryption with a user’s private key.
Security Requirements
- Traffic analysis
- Masquerade
- Content Modification
- Sequence Modification
- Timing Modification
Simple Hash functions
Firstly, the input is a sequence of n bits of blocks. Secondly, the input process one block at a time in an iterative way. Thirdly, XOR operation is done to produce the result.
For instance, Ci = bi1 + bi2 + … bin
SHA – Secure Hash Algorithm
SHA – 512:
Firstly, SHA 512 produces a output of 512 bit message digest. And the input is process in 1024 blocks. Here the message size is less than 2128 . The word size for SHA-512 is 64 bits.
SHA – 384:
Firstly, SHA 384 produces a output of 384 bit message digest. And the input is process in 1024 blocks. Here the message size is 2128 . The word size for SHA-384 is 64 bits.
SHA – 256:
Firstly, SHA 256 produces a output of 256 bit message digest. And the input is process in 512 blocks. Here the message size is less than 264 . The word size for SHA-256 is 32 bits.
SHA – 224:
Firstly, SHA 224 produces a output of 224 bit message digest. And the input is process in 512 blocks. Here the message size is 264 . The word size for SHA-224 is 32 bits.
SHA – 1:
Firstly, SHA 1 produces a output of 160 bit message digest. And the input is process in 512 blocks. Here the message size is 264 . The word size for SHA-1 is 32 bits.
Summary
In conclusion, we have learnt that Hash functions in cryptography takes a message of arbitary length and creates a message digest of fix length. We have also seen the various applications of hash functions in digital signature, message authentication and one way password file.
Lastly, we have learnt about secure hash algorithms which are SH1-1, SHA-224, SHA-256 etc.
[…] Using these concepts, a distributed firewall system operates as follows. A tool or a compiler is used to translate the policy language into an internal format. This policy data was provided by the system management tool to all of the hosts protected by the firewall. The arriving packets are then accepted or refused at each host based on the sender’s security policy and cryptographic verification. […]