LNPBP-81: additions to the draft

Author: dr-orlovsky

README.md

@@ -99,7 +99,7 @@ Criteria for a LNP/BP specification proposal:
 |    63 | Smart contracts | Prometheus+: prometheus over LN with tokenized RGB reputation                             | Standard      | Planned  |
 | 64-79 | *Reserved*      | *For the future use by lightning network protocol extensions*                             |               |          |
 |  [80] | Cryptography    | Merkle mountain ranges                                                                    | Standard      | Final    |
-|    81 | Cryptography    | Tagged merkle trees for client-side-validation                                            | Standard      | Draft    |
+|  [81] | Cryptography    | Tagged merkle trees for client-side-validation                                            | Standard      | Draft    |
 |    82 | Cryptography    | OpenTimestamps bitcoin transaction commitments                                            | Standard      | Final    |
 |    83 | Cryptography    | OpenTimestamps proof construction & verification                                          | Standard      | Final    |
 |    83 | Cryptography    | OpenTimestamps proof serialization                                                        | Standard      | Final    |

SUMMARY.md

@@ -7,12 +7,12 @@
 * [LNPBP-1: Public keys](lnpbp-0001.md)
 * [LNPBP-2: Script](lnpbp-0002.md)
 * [LNPBP-3: Tx output](lnpbp-0003.md)
+* [LNPBP-81: Tagged Merkle trees](lnpbp-0081.md)
 * [LNPBP-4: Multi-protocol](lnpbp-0004.md)
 * [LNPBP-6: PayTweak](lnpbp-0006.md)
 * [LNPBP-12: TapRet](lnpbp-0012.md)
 * [LNPBP-8: Single-use-seals](lnpbp-0008.md)
 * [LNPBP-10: TxO seals](lnpbp-0010.md)
-* [LNPBP-81: Tagged Merkle trees](lnpbp-0081.md)
 
 ## Bitcoin Protocol
 

lnpbp-0081.md

@@ -45,6 +45,20 @@ Based on bitcoin merklization with following modifications:
 
 ## Specification
 
+Merkle node is represented by a single SHA256 hash over the following data,
+serialized as a byte stream without any separators:
+- branch type (byte)
+- tag (128-bit number)
+- depth (byte)
+- width (4 bytes, little-endian)
+- child node 1 (32 bytes)
+- child node 2 (32 bytes)
+
+If one or both of the child nodes are absent, a constant consisting of 16 `0xFF`
+bytes is used.
+
+The root is produced via `CommitmentId` procedure
+
 ## Compatibility
 
 ## Rationale