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74 lines
2.2 KiB
Markdown
74 lines
2.2 KiB
Markdown
# DP3-T Implementation profile
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Against version 2020/4/8 of the whitepaper
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## Design 2
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### General
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Byte sequences are 8 bit octed strings.
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### Generating Empheral IDs
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The H is an SHA256 as per per RFC 6234
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TRUNKCATE128() takes the first 32 bytes (of the 64 byte SHA256)
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Test vector:
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Seed: 0000000000000000000000000000000000000000000000000000000000000000
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(i.e. 0x00, 0x00 .. 0x00 32 bytes)
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H (seed): 66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925
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TRUNKCATE128(H(seed)):
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66687aadf862bd776c8fc18b8e9f8e20
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### Local storare / handling of ‘t’
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‘t’ is a network order (big endian) unsigned 32 bit number. I.e. the number 1 is encoded transmitted as 0x00, 0x00, 0x00, 0x01 on the wire.
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‘t’ contains the unix UTC/Z timestamp as defined by RFC 3339.
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So the H(EphID||t) stored is a SHA256 taken over 16 + 4 = 20 sequentiel bytes in that order (EphID, then time).
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Test vector:
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Time: 2020-4-10 00:00:00 UTC
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T = 1586476800
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5E8FB700 (4 bytes)
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EphID || t =
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66687aadf862bd776c8fc18b8e9f8e201586476800) (16+4 butes)
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H(EphID || t)
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109708e29597623f56fd365ba92f1c717ca23994aabd7939822909c465cb10a5 (32 bytes)
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### Cuckoo filter and serialisation
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The depth of the Cuckoo filter shall be 4.
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The Cuckoo filter shall be serialised as:
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- Depth: unsigned 32 bit integer (A)
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- Number of slots: unsigned 32 bit integer (S)
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- Number of buckets: unsigned 32 bit integer (B)
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- Buckets B x ( A x slotsID)
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- with the slotID an unsigned 32 bit integer.
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- Slots(numbered 0 .. slotsID) S x ( key )
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- with the key a 31 bit unsigned int;
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- the topbit denotes a populated (0) or empty (1) slot.
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### Cuckoo filter publication
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The filter should be published prefixed by an RFC3161 timestamp.
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## Design 1
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The PRF used is HMAC-SHA256 as per RFC 6234 and RFC 2104 - and and where Skt_ is used as the `key’ and the string “broadcast key” (without trailing \0, i.e. exactly those 13 US-ASCII characters is the plaintext.
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The PRG used is AES128 in counter mode; with the IV set to a 128 bit unsigned number in network order (i.e the first IV is a byte array if [ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 ]) we start at 0, not 1
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and the plaintext 128 bits of 0’s.
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