According to Mosca's theorem with respect to migrating to PQC, a business asset may be vulnerable if _________, where “X” represents the number of years that data must be kept secure, “Y” is the estimated time needed to complete the transition, and "Z" is the expected time for a cryptographically relevant quantum computer to be built.单项选择题
A
a. X + Y = Z
B
b. X + Y > Z
C
c. X - Y < Z
D
d. X + Y < Z

Question

According to Mosca's theorem with respect to migrating to PQC, a business asset may be vulnerable if _________, where “X” represents the number of years that data must be kept secure, “Y” is the estimated time needed to complete the transition, and "Z" is the expected time for a cryptographically relevant quantum computer to be built.单项选择题

A

a. X + Y = Z

B

b. X + Y > Z

C

c. X - Y < Z

D

d. X + Y < Z

BlackTom AI · Accepted Answer

Mosca’s theorem compares three time intervals: the data’s required secrecy lifetime (X), the time needed to complete migration to post‑quantum cryptography (Y), and the estimated time until a cryptographically relevant quantum computer appears (Z). The theorem states an asset is vulnerable when the required secrecy lifetime plus the migration time exceeds the arrival time of a quantum computer — i.e., X + Y > Z. 1) Relevant knowledge points and concepts - X = number of years data must remain confidential. - Y = estimated years required to transition systems and deploy PQC. - Z = estimated years until a quantum computer capable of breaking current crypto is available. - If an adversary can capture current encrypted data and wait until a QC exists, they can decrypt it unless migration and any protective actions finish before the QC arrival relative to the data’s confidentiality window. 2) Step‑by‑step reasoning - Goal: ensure data remains secure for X years. - Migration takes Y years, so the earliest time by which all data will be protected under PQC is current time + Y (assuming migration starts immediately). - An adversary who records ciphertext today can decrypt it once a QC is available at time Z. - If the data must remain confidential for X years beyond now, the data remains sensitive until time X. - Combine the windows: if the quantum arrival Z occurs before the time at which the data becomes safe for its full confidentiality lifetime (which effectively is when migration finishes plus the remaining sensitive period), then the asset is vulnerable. 3) Intermediate/calculation example - Example values: X = 5 years (data sensitivity), Y = 3 years (migration), Z = 6 years (QC arrival). - Compute X + Y = 5 + 3 = 8 years. - Compare 8 > 6 → condition holds, so the asset is vulnerable because the QC arrives (year 6) before the combined window (year 8). 4) Why the correct answer is correct - X + Y > Z expresses that the combined requirement (data must remain secure for X years and you need Y years to complete migration) extends beyond the time a QC appears (Z). That means some sensitive data will be decryptable by the time a QC exists, so the asset is vulnerable. 5) Why the other options are incorrect - a. X + Y = Z: equality is a borderline case; Mosca’s practical test uses the strict “greater than” to indicate vulnerability (equality is not the standard criterion). - c. X - Y < Z: subtracting migration time from secrecy lifetime is not the relevant comparison and produces a meaningless ordering for vulnerability. - d. X + Y < Z: this indicates there is enough time to finish migration and keep data secure before QC arrival, so the asset would not be vulnerable. 6) Conclusion Therefore the correct vulnerability condition per Mosca’s theorem is X + Y > Z, matching the provided answer (b).

类似问题

The only algorithm selected so far by the NIST PQC process that is suitable for protecting data confidentiality is___.

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