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Episode #989 Quiz

Cascading Bloom Filters
Date: 2024-08-27 | Length: 1.75 hrs | Episode page at twit.tv

About this episode

Episode 989 covered supply-chain compromise risks from backdoored RFID access cards and counterfeit Cisco gear, plus SpinRite restoring SSD throughput by rewriting disturbed cells. Its main technical focus was Bloom filters: probabilistic set membership tests with no false negatives, then a three-stage CRLite cascade that uses Certificate Transparency data to enable local, instantaneous revocation checking.

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Question 1: In the episode’s explanation of the first-stage Bloom filter, what certificate attribute is converted into 20-bit chunks to choose which bits to set in the array?

Question 1

In the episode’s explanation of the first-stage Bloom filter, what certificate attribute is converted into 20-bit chunks to choose which bits to set in the array?

The certificate expiration timestamp The certificate subject common name The certificate serial number The certificate thumbprint hash

Question 2: According to the episode, what is the key operational reason a plain Bloom filter is not sufficient for certificate revocation checking?

Question 2

According to the episode, what is the key operational reason a plain Bloom filter is not sufficient for certificate revocation checking?

It can produce false positives but never false negatives It can produce false negatives but never false positives It can only represent small certificate lists efficiently It requires network queries to validate every match

Question 3: What did Mozilla say CRLite compresses when describing its revocation system in the January 2020 blog post referenced in the episode?

Question 3

What did Mozilla say CRLite compresses when describing its revocation system in the January 2020 blog post referenced in the episode?

About 30 MB of revocation data into about 300 KB About 3 GB of certificate data into about 30 MB About 300 MB of revocation data into about 1 MB About 1 GB of revocation data into about 300 MB

Question 4: How often does the episode say Firefox browsers reach out to obtain the latest CRLite bitmaps?

Question 4

How often does the episode say Firefox browsers reach out to obtain the latest CRLite bitmaps?

Every six hours Every hour Only when a revocation is encountered Every 24 hours

Question 5: According to the episode, what role does the third Bloom filter in the cascade play?

Question 5

According to the episode, what role does the third Bloom filter in the cascade play?

It trains the first filter on revoked certificates It stores the complete certificate transparency log locally It replaces the need for any earlier filters It serves as the final decision stage for ambiguous cases

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