The message digest must be authenticated it is easy

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The message digest must be authenticated •It is easy to compute the message digest. •It is impossible to reconstruct a message from a given digest. •It is infeasible to find two different messages with the same digest. The digest length (for a given hash function) is always the same (independently from the initial message length
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A successfully designed hash function should have the following four properties: 1. It is easy to compute the message digest. 2. It is impossible to reconstruct a message from a given digest. 3. It is infeasible to find two different messages with the same digest. 4. The digest length (for a given hash function) is always the same (independently from the initial message length
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Secure Hash Requirements H can be applied to a block of any size H produces a fixed-length output H( x ) is easy to compute Given h , it is infeasible to compute x s.t. H( x ) = h Given x , it is infeasible to find y s.t. H( x ) = H( y ) It is infeasible to find ( x , y ) such that H( x ) = H( y )
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Secure Hash Functions Message Digest v5 (MD5) 128-bit message digest has been found to have collision weakness Secure Hash Algorithm (SHA-1) 160-bit message digest
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: Keyed hash functions algorithms currently considered as secure Hash length Key Length Algorithm 160 bits 160 bits HMAC-SHA 160 bits 160 bits HMAC-RIPemd-160
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IPv4 and IPv6 Security Provides encryption/authentication at the network (IP) layer IPSec applications: Virtual Private Networking E-commerce
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