Information Security · Unit 5
Hash Functions and Message Authentication
Exam-focused notes for Hash Functions and Message Authentication (Information Security, BIT303): what the TU syllabus asks and how it has actually been tested, with 7 solved past questions from this unit.
What this unit covers
- Hash function properties and design
- MD5 algorithm and hash value generation
- SHA-1 algorithm and padding
- SHA-2 hash function
- Message authentication purposes
- Digital signatures for authentication
Message authentication purposes
What are the purposes of message authentication? Explain the working mechanism of MD5.[10]
--- Message authentication is a mechanism used to verify the integrity and origin of a message. The main purposes are: Ensures that the message has not been altered (accidentally or intentionally) during transmission. The receiver can verify that the receiv...
Full solved answer →SHA-2 hash function
How hash value is generated by the SHA-2 hash function. [5]
Note: No specific reference notes were found for this topic. The following answer is based on standard cryptography curriculum content appropriate for BSc CSIT. --- SHA-2 (Secure Hash Algorithm 2) is a family of cryptographic hash functions designed by the ...
Full solved answer →SHA-1 algorithm and padding
Describe the role of hash functions in authenticating message? How SHA-1 algorithm is used to produce hash value of a message? Explain.[10]
A hash function H is a mathematical function that maps a variable-length input message M to a fixed-length output called the message digest or hash value. The basic authentication process works as follows: At the Sender Side: 1. Sender computes hash value: ...
Full solved answer →SHA-1 Hash Function Properties and Computation
What are properties of hash function? In a hash function SHA-1, how padded message is computed before hash function computation? Using elongated message blocks from $w_0$ to $w_{79}$ how can you compute the final hash value? For the 160 bit hash value represented by 5 words A, B, C, D, E, write the expressions for $A_{79}$, $B_{79}$, $C_{79}$ after the last pass of the algorithm?[10]
- Hash algorithm: SHA-1 - Output size: 160-bit hash, represented as five 32-bit words $A, B, C, D, E$ - Message schedule words: $w0$ to $w{79}$ (80 words) - Required: properties of hash functions, padding procedure, hash computation, and expressions for $A{...
Full solved answer →Digital signatures for authentication
What is the role of digital signature in message authentication? List any two natures of zombies. [5]
--- A digital signature is a cryptographic mechanism that provides a way to verify the authenticity and integrity of a digital message or document. It plays the following key roles in message authentication: A digital signature confirms the identity of the ...
Full solved answer →What is digital signature? How it can be used for message authentication? [5]
A digital signature is an electronic equivalent of a handwritten signature that provides a way to authenticate the identity of the sender of a message or the signer of a document. It is a cryptographic mechanism that uses asymmetric (public-key) cryptograph...
Full solved answer →MD5 algorithm and hash value generation
What is hash function? Describe how 128-bit of hash value is generated by taking an input message of variable size using MD5 algorithm?[10]
A hash function is a mathematical function that takes a variable-length input message and produces a fixed-length output called the hash value or message digest, which acts as a digital fingerprint of the original message. Property Description ------ Variab...
Full solved answer →Make Unit 5 stick
Practice BIT303 with flashcards & quizzes