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Questions and Answers
What does MD5 stand for?
Message-Digest Algorithm 5
Who invented the MD5 algorithm?
Ronald Rivest
Which of the following algorithms preceded MD5? (Select all that apply)
MD5 has never shown any vulnerabilities.
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What is the output size of the MD5 hash?
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What is one key property of a cryptographic hash function like MD5?
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The length of the message after padding for MD5 should be congruent to ______ mod 512.
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Match the following MD5 buffer values with their hexadecimal integer values:
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How many operations does the MD5 algorithm perform in total?
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Study Notes
Message-Digest Algorithm 5 (MD5)
- MD5 (Message-Digest Algorithm 5) is a cryptographic hash function that generates a 128-bit hash from any input.
- Ronald Rivest invented MD5 in 1991 as an improvement on its predecessor, MD4, which had known vulnerabilities.
- MD5 was widely used for digital signatures, checksum calculations, and file integrity verification.
- MD5 has been replaced in many applications by more secure algorithms due to vulnerabilities like collisions attacks.
History and Development
- MD5 is the fifth algorithm in a series of message-digest algorithms designed by Ronald Rivest.
- MD5 was developed to address weaknesses found in its predecessor, MD4.
- MD4, the predecessor, was vulnerable to Collision attacks, which led to the creation of MD5.
- MD5 aimed to prevent vulnerabilities found in MD4 by making changes to data processing and internal structure.
- MD5 itself became vulnerable to attacks in the late 1990s, and by the early 2000s, it was considered broken for cryptographic use.
Technical Details and How MD5 Works
- MD5 is a hash function, taking any input and producing a fixed-size 16-byte (128-bit) output.
- MD5 has four key properties as a cryptographic hash function:
- Deterministic: The same input always produces the same output.
- Pre-image resistance: Given an output, it's nearly impossible to find the original input.
- Small changes to input produce drastically different outputs: Even a tiny input change leads to a completely different hash.
- Fixed output size: Regardless of the input size, the output is always 128 bits (16 bytes).
MD5 Processing Stages
- MD5 processes data in 512-bit blocks, and uses padding to ensure input sizes are multiples of 512 bits.
- Padding adds a "1" bit, then enough "0" bits to reach the required length.
- After padding, the original message length is appended in a 64-bit representation.
- MD5 uses four 32-bit buffers (A, B, C, D), initialized to specific hex values:
- A = 0x67452301
- B = 0xefcdab89
- C = 0x98badcfe
- D = 0x10325476
- MD5 processes the message in 512-bit chunks, divided into 16 32-bit words.
- Each chunk is processed in four rounds, and each round has 16 operations, totaling 64 operations.
- The operations mainly use:
- Four non-linear functions (F, G, H, I) to process each block.
- Bitwise operations (XOR, AND, OR) and shifts to scramble the input.
- Modular addition used to combine constants and previous operation results.
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Description
Explore the Message-Digest Algorithm 5 (MD5), a widely used cryptographic hash function developed by Ronald Rivest in 1991. Learn about its history, development, and the vulnerabilities that led to the creation of more secure algorithms. This quiz covers essential concepts and the evolution of MD5 in digital security.
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