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# DP3-T Implementation profile
Against version 2020/4/8 of the whitepaper
## Design 2
### General
Byte sequences are 8 bit octed strings.
### Generating Empheral IDs
The H is an SHA256 as per per RFC 6234
TRUNKCATE128() takes the first 32 bytes (of the 64 byte SHA256)
Test vector:
Seed: 0000000000000000000000000000000000000000000000000000000000000000
(i.e. 0x00, 0x00 .. 0x00 32 bytes)
H (seed): 66687aadf862bd776c8fc18b8e9f8e20089714856ee233b3902a591d0d5f2925
TRUNKCATE128(H(seed)):
66687aadf862bd776c8fc18b8e9f8e20
### Local storare / handling of ‘ ’
‘ ’
‘ ’
So the H(EphID||t) stored is a SHA256 taken over 16 + 4 = 20 sequentiel bytes in that order (EphID, then time).
Test vector:
Time: 2020-4-10 00:00:00 UTC
T = 1586476800
5E8FB700 (4 bytes)
EphID || t =
66687aadf862bd776c8fc18b8e9f8e201586476800) (16+4 butes)
H(EphID || t)
109708e29597623f56fd365ba92f1c717ca23994aabd7939822909c465cb10a5 (32 bytes)
### Cuckoo filter and serialisation
The depth of the Cuckoo filter shall be 4.
The Cuckoo filter shall be serialised as:
- Depth: unsigned 32 bit integer (A)
- Number of slots: unsigned 32 bit integer (S)
- Number of buckets: unsigned 32 bit integer (B)
- 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;
- the topbit denotes a populated (0) or empty (1) slot.
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### Cuckoo filter publication
The filter should be published prefixed by an RFC3161 timestamp.
## Design 1
The PRF used is HMAC-SHA256 as per RFC 6234 and RFC 2104 - and and where Skt_ is used as the `key’
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
and the plaintext 128 bits of 0’
