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Crypto Hashes and PKI Cryptography Assignment

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Added on  2020-10-09

Crypto Hashes and PKI Cryptography Assignment

   Added on 2020-10-09

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Week 2 Lecture 2 - Crypto Hashes and PKI1Week 2 Lecture 2 - Crypto Hashes and PKICryptography UsesWe know that the Diffie Hellman algorithm is primarily used for key exhange and RSA is used for authentication. However, there are many other algorithms which can be used for intergrity checks, privacy, authentication or data exchange.Cryptography HashesA cryptographic hash has function h maps an arbitrary length input x into an output h(x) of a fixed length n. This is compression and it should be computationally easy to produce h(x) from x.Manipulation Detection Codes MDCs) or Message Integrity Codes MICs) can detect changes to a document.From a security perspective, we want:Pre-image Resistance (one way function): for a given y, it is computationally infeasible to find x such that h(x) = y.Second Pre-Image Resistance (weak collision resistance): given input x and h(x) it is computationally infeasible to find another x', x<>x' with h(x) = h(x').Collision Resistance (strong collision resistance): it is computationally infeasible to find any two inputs x and x', x<>x' such that h(x) = h(x').Message DigestA One Way Hash Function (a.ka OWHF) has compression, fast computation and first and second pre-image resistance.It has functions that are often called Message Digests in security or hash values or checksums (but not the network checksums).In a compression function, an input x if broken into blocks or of a set block size with padding as neccessary in the last block. The hash is then a repeated application of the compression function.x , x , ..., x12n
Crypto Hashes and PKI Cryptography Assignment_1
Week 2 Lecture 2 - Crypto Hashes and PKI2Message Authentication CodeA message Authentication Code gives assurance about the source (authentication) and integrity of the message.A MAC is generated from the message and a cryptographic key is essentially a keyed hash function. Authentication occurs through receiver knowing the sender's key.Digital Signature AlgorithmThe DSA is a US Federal Information Processing Standard FIPS , later adopted by NIST as part of the Digital Signature Standard DSS .The DSS assumes a prime p of 1024 bits, and a q dividing (p-1) (key length) of 160 bits. The hash funcntion used is SHA 1.Digital SignaturesA company or person's public key is bound up with their identity into a certificate, The certificate is then verified or authenticated by a Certificate Authority or Trusted Third Party TTP . Certifictaes are valid for only a short time, and can be revoked.A Digital Certificate maust be shown to be unforgeable, authentic, unalterable and be non-reusable. So, it is a file:with a hash known as a message digest, (integrity)with a sender's private encryption key, (authenticity)with a label to show the identity of the sender.A timestamp also helps with non-reputation (where the sender cannot deny or repudiate it was they who sent the message.Digital FingerprintA hash is made of the original message which validates the integrity of the message. Hashes can be 128 or 1216 bits, and the algorithms used are the MD series or the SHA series. Hashes are also called cryptographic checksum, one way hash functions or message integrity checks MICs).Digital Signature (Sender)After a message is hashed (for integrity), it is then encrypted with the user's Private key to create a digital signature. Expiration dates, serial numbers etc
Crypto Hashes and PKI Cryptography Assignment_2

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