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Episode #964 Quiz

PQ3
Date: 2024-03-05 | Length: 2 hrs | Episode page at twit.tv

About this episode

Apple’s PQ3 upgrades iMessage with hybrid post-quantum and elliptic-curve cryptography, using Kyber768 for initial key establishment and periodic rekeying. Device-generated public keys live in Secure Enclave, while formal verification with Tamarin and game-based proofs claims secrecy and authenticity. Rekeying overhead exceeds 2 KB, so it amortizes roughly every 50 messages or weekly.

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Question 1: According to the episode, what fixed-size transformation did Steve recommend for handling a backend that only accepts an 8-character password drawn from a 64-character alphabet?

Question 1

According to the episode, what fixed-size transformation did Steve recommend for handling a backend that only accepts an 8-character password drawn from a 64-character alphabet?

Truncate the password to eight characters, then append a salt Normalize the password to ASCII, then pad it to eight characters Encrypt the password first, then base64-encode the ciphertext Hash the password first, then map the hash into six-bit chunks

Question 2: What did Apple say was the main reason PQ3 does not use the post-quantum ratchet on every message?

Question 2

What did Apple say was the main reason PQ3 does not use the post-quantum ratchet on every message?

The formal verification tools cannot model per-message rekeying The Kyber-based ratchet adds more than two kilobytes per message The ECDH ratchet fails whenever the receiver is offline The Secure Enclave cannot store more than one quantum key

Question 3: How did Steve characterize the relationship between Signal's prior design and Apple's claim that PQ3 uniquely reaches Level 3 security?

Question 3

How did Steve characterize the relationship between Signal's prior design and Apple's claim that PQ3 uniquely reaches Level 3 security?

Signal uses post-quantum keys only for sender authentication Signal lacked any forward secrecy until Apple announced PQ3 Signal depends on periodic password resets instead of key rotation Signal already had the ratchet property through its Double Ratchet design

Question 4: What did Steve recommend Robert do after the company failed to properly address the vulnerable server-banner issue?

Question 4

What did Steve recommend Robert do after the company failed to properly address the vulnerable server-banner issue?

Publish the vulnerability details immediately on social media Submit the evidence to CISA and let them handle it Continue negotiating directly until the company updates all sites Accept the $350 bounty and keep silent about the issue

Question 5: What did Apple say its PQ3 design uses for the initial post-quantum key establishment?

Question 5

What did Apple say its PQ3 design uses for the initial post-quantum key establishment?

Kyber public keys registered with the device ECDSA signatures generated by Apple servers SHA-512 digests derived from contact verification data RSA public keys rotated through the Secure Enclave

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