3.1 : Message encryption, message authentication code, hashfunction3.2 : An authenticator that is a cryptographic work of both theinformation to be authenticated and a mystery key.3.3: A, A hash code is computed from the source message, scrambledutilizing symmetric encryption and a mystery key (B), This is the same methodas in (a) but that public-key encryption is utilized; the sender scrambles thehash code with the sender’s private key, and the recipient decodes the hashcode with the sender’s open key. (c) A mystery esteem is added to a message andat that point a hash code is calculated utilizing the message additionallymystery esteem as input. At that point the message (without the mystery esteem)and the hash code are transmitted3.4: a – H can be connected to a square of information of anymeasure.
b- For any given esteem h, it is computationally infeasible todiscover x such that H(x) = h. This is some of the time alluded to in thewriting as the one-way property.c- It is computationallyinfeasible to discover any combine (x, y) such that H(x) = H(y).3.5 : Thecompression work is the essential module, or fundamental building piece, of ahash work.
The hash work comprises of iterated application of the compressionwork.3.6: Plaintext, Encryption algorithm, Public and private keys,Ciphertext, Decryption algorithm3.7 : a – Encryption/decryption: The sender scrambles a messagewith the recipient’s open keyb- Digital signature: The sender “signs” a message withits private key. Marking is accomplished by a cryptographic calculationconnected to the message or to a little piece of information that is a work ofthe message.c- Key exchange: Two sides participate to trade a session key.
Afew diverse approaches are conceivable, including the private key(s) of one orboth parties.3.8: The key utilized in ordinary encryption is regularly alludedto as a mystery key.
The two keys utilized for public-key encryption arealluded to as the open key and the private key.3.9: digital signature: is an verification instrument that empowersthe maker of a message to join a code that acts as a signature. The signatureis shaped by taking the hash of the message and scrambling the message with thecreator’s private key. The signature ensures the source and astuteness of themessage.