What percentage of the keyspace should be brute-forced to find an equivalent key if the block cipher has?

phantomcraft

6/9/23, 4:10 AM

I have been reading the Hasty Pudding Cipher specification and the author make clear that the cipher has some equivalent keys if the keyspace is larger than 8192-bits:

Two keys are equivalent if they expand to the same key-expansion
table.  The likelihood is negligible for keys of size < 1/2 the
key-expansion table size, 8192 bits.  For keys longer than this, some
will be equivalent, but there is no feasible way to discover an
equivalent key pair.

My question is? What percentage of keyspace of an block cipher should be brute-forced to find an equivalent key (if the cipher has equivalent keys)?

0 + 0

block-cipher

keys

kelalaka

6/9/23, 10:30 AM

`but there is no feasible way to discover an equivalent key pair.`. Are you asking for an answer for this?

phantomcraft

6/9/23, 2:05 PM

@kelalaka Yes. It's valid.

fgrieu

6/9/23, 9:06 PM

Is it looked at an answer independent of the block cipher (with equivalent keys), considered as a black box; or is the question geared only at HPC? In the second case, what restriction (if any) does "brute-forced" imply? Does the question boil down to: what would be the effort to discover an equivalent key pair for HPC?

Elon Musk

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EN: What percentage of the keyspace should be brute-forced to find an equivalent key if the block cipher has?

TH: เปอร์เซ็นต์ของคีย์สเปซควรถูกบังคับให้เดรัจฉานเพื่อค้นหาคีย์ที่เทียบเท่าหากรหัสบล็อกมี

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RU: Какой процент пространства ключей следует перебрать, чтобы найти эквивалентный ключ, если он есть в блочном шифре?

VI: Bao nhiêu phần trăm không gian khóa sẽ bị ép buộc để tìm một khóa tương đương nếu mật mã khối có?

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