diff --git a/Castor/Sources/Castor.swift b/Castor/Sources/Castor.swift
deleted file mode 100644
index 1a0a45df..00000000
--- a/Castor/Sources/Castor.swift
+++ /dev/null
@@ -1 +0,0 @@
-// This file is just here as a foolproof/template since for Swift Packages a module source always have to have at least one Swift file
diff --git a/Castor/Sources/CastorImpl+Public.swift b/Castor/Sources/CastorImpl+Public.swift
new file mode 100644
index 00000000..bd4968f1
--- /dev/null
+++ b/Castor/Sources/CastorImpl+Public.swift
@@ -0,0 +1,7 @@
+import Domain
+
+extension CastorImpl: Castor {
+    public func parseDID(str: String) throws -> DID {
+        try DIDParser(didString: str).parse()
+    }
+}
diff --git a/Castor/Sources/CastorImpl.swift b/Castor/Sources/CastorImpl.swift
new file mode 100644
index 00000000..a7e49acb
--- /dev/null
+++ b/Castor/Sources/CastorImpl.swift
@@ -0,0 +1 @@
+public struct CastorImpl {}
diff --git a/Castor/Sources/DIDParser.swift b/Castor/Sources/DIDParser.swift
new file mode 100644
index 00000000..1bb5a2dd
--- /dev/null
+++ b/Castor/Sources/DIDParser.swift
@@ -0,0 +1,56 @@
+import Antlr4
+import Domain
+import Foundation
+
+struct DIDParser {
+    struct InvalidDIDStringError: Error {}
+
+    let didString: String
+
+    func parse() throws -> DID {
+        let inputStream = ANTLRInputStream(didString)
+        let lexer = DIDAbnfLexer(inputStream)
+        let tokenStream = CommonTokenStream(lexer)
+
+        let parser = try DIDAbnfParser(tokenStream)
+        parser.setErrorHandler(BailErrorStrategy())
+        let context = try parser.did()
+
+        let listener = Listener()
+        try ParseTreeWalker().walk(listener, context)
+
+        guard
+            let schema = listener.scheme,
+            let methodName = listener.methodName,
+            let methodId = listener.methodId
+        else { throw InvalidDIDStringError() }
+
+        let did = DID(
+            schema: schema,
+            method: methodName,
+            methodId: methodId
+        )
+
+        return did
+    }
+}
+
+fileprivate final class Listener: DIDAbnfBaseListener {
+    fileprivate var scheme: String?
+    fileprivate var methodName: String?
+    fileprivate var methodId: String?
+
+    override func exitDid(_ ctx: DIDAbnfParser.DidContext) {
+        ctx.SCHEMA().map { scheme = $0.getText() }
+    }
+
+    override func exitMethod_name(_ ctx: DIDAbnfParser.Method_nameContext) {
+        methodName = ctx.getText()
+    }
+
+    override func exitMethod_specific_id(
+        _ ctx: DIDAbnfParser.Method_specific_idContext
+    ) {
+        methodId = ctx.getText()
+    }
+}
diff --git a/Castor/Tests/DIDParserTests.swift b/Castor/Tests/DIDParserTests.swift
new file mode 100644
index 00000000..b10b49c0
--- /dev/null
+++ b/Castor/Tests/DIDParserTests.swift
@@ -0,0 +1,41 @@
+import XCTest
+@testable import Castor
+
+final class DIDParserTests: XCTestCase {
+
+    func testValidDIDs() throws {
+        let didExample1 = "did:aaaaaa:aa:aaa"
+        let didExample2 = "did:prism01:b2.-_%11:b4._-%11"
+        let didExample3 = "did:prism:b6c0c33d701ac1b9a262a14454d1bbde3d127d697a76950963c5fd930605:Cj8KPRI7CgdtYXN0ZXIwEAFKLgoJc2VmsxEiECSTjyV7sUfCr_ArpN9rvCwR9fRMAhcsr_S7ZRiJk4p5k"
+        
+        let parsedDID1 = try DIDParser(didString: didExample1).parse()
+        let parsedDID2 = try DIDParser(didString: didExample2).parse()
+        let parsedDID3 = try DIDParser(didString: didExample3).parse()
+        
+        XCTAssertEqual(parsedDID1.schema, "did")
+        XCTAssertEqual(parsedDID1.method, "aaaaaa")
+        XCTAssertEqual(parsedDID1.methodId, "aa:aaa")
+        
+        XCTAssertEqual(parsedDID2.schema, "did")
+        XCTAssertEqual(parsedDID2.method, "prism01")
+        XCTAssertEqual(parsedDID2.methodId, "b2.-_%11:b4._-%11")
+        
+        XCTAssertEqual(parsedDID3.schema, "did")
+        XCTAssertEqual(parsedDID3.method, "prism")
+        XCTAssertEqual(parsedDID3.methodId, "b6c0c33d701ac1b9a262a14454d1bbde3d127d697a76950963c5fd930605:Cj8KPRI7CgdtYXN0ZXIwEAFKLgoJc2VmsxEiECSTjyV7sUfCr_ArpN9rvCwR9fRMAhcsr_S7ZRiJk4p5k")
+    }
+    
+    func testInvalidDIDs() throws {
+        let didExample1 = "idi:aaaaaa:aa:aaa"
+        let didExample2 = "did:-prism-:aaaaa:aaaa"
+        let didExample3 = "did:prism:aaaaaaaaaaa::"
+        let didExample4 = "did::prism:aaaaaaaaaaa:aaaa"
+        let didExample5 = "did:prism::aaaaaaaaaaa:aaaa"
+        
+        XCTAssertThrowsError(try DIDParser(didString: didExample1).parse())
+        XCTAssertThrowsError(try DIDParser(didString: didExample2).parse())
+        XCTAssertThrowsError(try DIDParser(didString: didExample3).parse())
+        XCTAssertThrowsError(try DIDParser(didString: didExample4).parse())
+        XCTAssertThrowsError(try DIDParser(didString: didExample5).parse())
+    }
+}
diff --git a/Domain/Sources/BBs/Castor.swift b/Domain/Sources/BBs/Castor.swift
new file mode 100644
index 00000000..75fdac09
--- /dev/null
+++ b/Domain/Sources/BBs/Castor.swift
@@ -0,0 +1,3 @@
+public protocol Castor {
+    func parseDID(str: String) throws -> DID
+}