English
Menu

Hardware Security: Advanced Topics and Trends

What is wrong with the idea that "if ECC memory is used, there is no need to worry about Rowhammer"?

  1. ACommon ECC (SECDED) corrects only a 1-bit error per word, and when many bits flip it may be unable to correct or even detect the error
  2. BECC only slows down data reads and does not have any function to correct bits that have flipped in memory in the first place
  3. CPlacing ECC check bits increases the number of rows and narrows the spacing of activated rows, making Rowhammer twice as likely
Show answer and explanation

Answer: A. Common ECC (SECDED) corrects only a 1-bit error per word, and when many bits flip it may be unable to correct or even detect the error

SECDED ECC as used in servers adds 8 check bits to 64 data bits, corrects 1-bit errors and detects 2-bit errors. With Rowhammer, three or more bits can flip in the same word, and then the error may go unnoticed or be mistaken for another value and wrongly corrected. ECC is an effective layer that suppresses many flips, but it must be combined with countermeasures that prevent the flips themselves, such as TRR and refresh management.

  • A. Correct. It cannot handle more flips than its correction capability.
  • B. ECC can correct 1-bit errors. Its limit lies in cases where many bits flip at once.
  • C. Using ECC does not change how likely Rowhammer is.
Practice this topic Back to topic

Books on Hardware Security: Advanced Topics and Trends Ad

As an Amazon Associate I earn from qualifying purchases.

More Hardware Security: Advanced Topics and Trends questions

  1. Which correctly describes the idea of PRAC (per-row activation counting), added to the DDR5 standard updated in 2024 (JESD79-5C)?
  2. For simplicity, take the shortest interval at which rows in the same bank can be activated to be tRC = 50 ns. With a refresh period of 64 ms, the maximum number of times a neighbouring row can be activated between one refresh of a given row and the next is 64 ms ÷ 50 ns. What is this maximum number when the refresh rate is doubled?
  3. Which correctly describes the characteristics of the vulnerability called MDS (Microarchitectural Data Sampling), published in 2019?
  4. Which correctly pairs the descriptions of retpoline and IBRS, countermeasures against the Spectre variant that abuses indirect branch prediction (branch target injection)?
  5. A task took 10 seconds before mitigations for speculative execution were applied and made 5 million system calls during that time. Assume that the mitigations increase the processing time per system call from 0.4 µs to 0.6 µs and leave the time of everything else unchanged. By what proportion does the total time of the task increase?