Add NIP-03: OpenTimestamps proof in events

Cargo.toml

@@ -39,3 +39,4 @@ reqwest = { version = "0.11", default-features = false, features = ["json", "rus
 tokio = { version = "1.24", optional = true, features = ["macros"] }
 futures-util = { version = "0.3", optional = true }
 futures = { version = "0.3", optional = true }
+nostr-ots = "0.1.1"

src/events.rs

@@ -137,6 +137,7 @@ impl EventPrepare {
             tags: self.tags.clone(),
             content: self.content.clone(),
             sig: signature,
+            ots: None,
         }
     }
 }
@@ -160,12 +161,18 @@ pub struct Event {
     pub content: String,
     /// 64-bytes signature of the sha256 hash of the serialized event data, which is the same as the "id" field
     pub sig: String,
+    /// OpenTimestamps proof serialized in base64
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ots: Option<String>,
 }
 
 #[derive(Error, Debug, Eq, PartialEq)]
 pub enum EventError {
     #[error("Secp256k1 Error: {}", _0)]
     Secp256k1Error(secp256k1::Error),
+
+    #[error("Ots error: {0}")]
+    Ots(String),
 }
 
 impl From<secp256k1::Error> for EventError {
@@ -254,6 +261,14 @@ impl Event {
         )?;
         Ok(())
     }
+
+    /// Initialize the ots optional field in this event with the OpenTimestamps proof, 
+    /// according to NIP-03
+    pub fn timestamp(&mut self) -> Result<(), EventError> {
+        let ots = nostr_ots::timestamp_event(&self.id).map_err(|e| EventError::Ots(e.to_string()))?;
+        self.ots = Some(ots);
+        Ok(())
+    }
 }
 
 impl fmt::Display for Event {