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+# tinySSB test vectors: GoSET
+
+This file and directory contains some test vectors that emerge when
+two peers synchronize their sets of feed IDs (FID). There is are two
+message types in the synchronization protocol for which we provide
+test vectors: ```novelty``` and ```claim```.
+
+## Notation
+
+We use [s-expressions](https://www.ietf.org/archive/id/draft-rivest-sexp-13.html) for representing constants, data records, sequences and packets.
+
+A packet instance is first written in symbolic form by giving
+the encoding function and its parameters. Separated by ```===```,
+we then show the resulting byte sequence (test vector). Example:
+
+```
+(NOVELTY_ENCODE #...7_DMX_bytes...#
+                "N"
+                #...32_novelty_bytes...#)
+===
+#....#
+```
+
+The hex digits of a long byte sequences may wrap at the line end.
+
+
+## The Two GoSET Packet Types
+
+### Novelty
+
+A ```novelty``` message is used to announce a new FID. It has three fields:
+
+```
+dmx   7B DMX value for the GoSET protocol (constant value)
+t     1B packet type (fixed to 'N' for a novelty)
+f    32B FID
+```
+
+which results in a packet with 40 bytes. It is assumed that the link
+media provides the packet's length and verifies the integrity of the
+```novelty``` packet (using some CRC value) before processing it.
+
+Using a ```novelty``` message is necessary when a peer only knows
+about one FID. ```Novelty``` packets can also be used when a node can
+assume that its peers do _not_ know yet about a FID. This is
+beneficial because it avoids the set reconciliation process via
+```claim``` messages.
+
+### Claim
+
+A ```claim``` message has five fields:
+```
+dmx   7B DMX value for the GoSET protocol (constant value)
+t     1B packet type (fixed to 'C' for a claim)
+f1   32B smallest known FID
+f2   32B highest known FID
+fx   32B XOR of all known FIDs
+cnt   1B number of known FIDs (0..255)
+```
+
+which results in a packet with 105 bytes. It is assumed that the link
+media provides the packet's length and verifies the integrity of the
+```claim packet``` (using some CRC value) before processing it.
+
+The ```dmx``` field for all GoSET packets is a constant and is
+computed as the first 7 bytes of the SHA256 value of the ASCII string
+
+```
+tinySSB-0.1 GOset 1
+```
+
+with length 19. The value is:
+
+```
+GoSET_DMX
+===
+#??????????????#
+```
+
+
+## Four Scenarios:
+
+Peer A knows about five feeds:
+```
+#1000001f4fb57f5d84506379a31c0ab5f24c435c63f2df9b8c373817975eed1f#
+#020000a391c773f2e9e22b03df4731b64616024bbd2893f436db8fc1c922d5e8#
+#003000142e693f47f7b09940552bc05a58282491e3f09fa19749fabf500f4990#
+#000400eb4dadc66e1d871278fe92aa1f4e52e7e64bda6fda52b8623ab887785a#
+#0000502302156b0061f1ca08d296d2367cfb40c88c005b73413bc394c4022aca#
+```
+
+Initially, peer B only knows about its own feed:
+```
+#0000069ee3e69964fc50391b1c1d80e918a419f3a592a8eb80cfc549dc61be99#
+```
+
+### case a) Peer A sends a ```claim``` about its five feeds (#1 to #5)
+
+```
+(CLAIM_ENCODE #...7_DMX_bytes...#
+              "C"
+              #1000001f4fb57f5d84506379a31c0ab5f24c435c63f2df9b8c373817975eed1f#
+              #0000502302156b0061f1ca08d296d2367cfb40c88c005b73413bc394c4022aca#
+              #??...??#
+              #05#)
+===
+#???#
+```
+
+### case b) Peer B sends a ```claim``` about its single feed (#6)
+
+...
+
+
+### case c) Peer A reacts after including feed #6 into its set
+
+...
+
+
+### case d) Peer B reacts after including feeds #1 and #5
+
+...
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