Slide an toàn và hệ thống bảo mật thông tin chapter 7 cryptographic hash funtions

.c om cu u du o ng th an co ng CRYPTOGRAPHIC HASH FUNTIONS CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Contents Hash function 2) Applications of Cryptographic Hash Functions 3) Simple Hash Functions 4) Requirements and Security 5) Secure Hash Algorithm (SHA) cu u du o ng th an co ng 1) CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Hash function cu u du o ng th an co value, or message digest: h= H(M) ng  A hash function maps a variable-length message into a fixed-length hash CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Cryptographic hash function  A cryptographic hash function is an algorithm for which it is co ng computationally infeasible to find either a data object that maps to a pre- cu u du o ng th an specified hash result or two data objects that map to the same hash result CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Applications Of Cryptographic Hash Functions ng  Message Authentication cu u du o ng th an co  Digital signature CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Message Authentication  Message authentication is a mechanism or service used to verify the co ng integrity of a message Message authentication assures that data received cu u du o ng th an are exactly as sent CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om Message Authentication CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Digital signature  The hash value of a message is encrypted with a user’s private key co ng  Anyone who knows the user’s public key can verify the integrity of the cu u du o ng th an message that is associated with the digital signature CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Other Applications ng  Hash functions are commonly used to create a one-way password file cu u du o ng th an co  Hash functions can be used for intrusion detection and virus detection CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Simple Hash Functions ng  Input (message, file,etc.) is viewed as a sequence of n-bit blocks co  One of the simplest hash functions is the bit-by-bit exclusive-OR (XOR) cu u du o ng th an of every block This can be expressed as: CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om Requirements And Security CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om Secure Hash Algorithm (SHA) CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om SHA-512 CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om SHA-512  Step Append padding bits: The padding consists of a single bit co ng followed by the necessary number of bits th an  Step Append length: A block of 128 bits is appended to the message ng This block is treated as an unsigned 128-bit integer and contains the length cu u du o of the original message (before the padding) CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om SHA-512  Step Initialize hash buffer: A 512-bit buffer is used to hold intermediate co ng and final results of the hash function The buffer can be represented as an eight 64-bit registers (a, b, c, d, e, f, g, h) These registers are initialized to cu u du o ng th the following 64-bit integers (hexadecimal values): CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om SHA-512 cu u du o ng th an co ng  Step Process message in 1024-bit (128-word) blocks: CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om SHA-512  Each round also makes use of an additive constant, where indicates one of cu u du o ng th an co ng the 80 rounds CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om SHA-512 CuuDuongThanCong.com https://fb.com/tailieudientucntt cu u du o ng th an co ng c om SHA-512: Word Expansion CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om SHA-512  Step Output: After all 1024-bit blocks have been processed, the output cu u du o ng th an co ng from the Nth stage is the 512-bit message digest CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om ng co an th ng du o u cu CuuDuongThanCong.com https://fb.com/tailieudientucntt ... Contents Hash function 2) Applications of Cryptographic Hash Functions 3) Simple Hash Functions 4) Requirements and Security 5) Secure Hash Algorithm (SHA) cu u du o ng th an co ng 1) CuuDuongThanCong.com... Cryptographic hash function  A cryptographic hash function is an algorithm for which it is co ng computationally infeasible to find either a data object that maps to a pre- cu u du o ng th an. .. password file cu u du o ng th an co  Hash functions can be used for intrusion detection and virus detection CuuDuongThanCong.com https://fb.com/tailieudientucntt .c om Simple Hash Functions ng  Input