diff --git a/src/extractTBS.ts b/src/extractTBS.ts
new file mode 100644
index 0000000..610a861
--- /dev/null
+++ b/src/extractTBS.ts
@@ -0,0 +1,18 @@
+import cbor from "./cbor"
+import { EMPTY_BUFFER } from './lib/common'
+
+export const extractTBS = (message: Uint8Array) => {
+  const { tag, value } = cbor.decode(message)
+  if (tag !== 18) {
+    throw new Error('only cose sign 1 is supported')
+  }
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  const [protectedHeaderBytes, unprotectedHeaderMap, payloadBuffer] = value
+  const tbs = cbor.encode([
+    'Signature1',
+    protectedHeaderBytes,
+    EMPTY_BUFFER,
+    payloadBuffer
+  ]);
+  return tbs
+}
\ No newline at end of file
diff --git a/src/index.ts b/src/index.ts
index 1ec7399..6412bad 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -23,8 +23,11 @@ import * as lib from './lib'
 
 import * as scitt from './scitt'
 
+import { extractTBS } from './extractTBS'
+
 const cose = {
   key,
+  extractTBS,
   scitt,
   lib,
   utils,
diff --git a/src/scitt/identifiers/index.ts b/src/scitt/identifiers/index.ts
new file mode 100644
index 0000000..6afa0f7
--- /dev/null
+++ b/src/scitt/identifiers/index.ts
@@ -0,0 +1 @@
+export * from './urn'
\ No newline at end of file
diff --git a/src/scitt/identifiers/scitt-identifiers.test.ts b/src/scitt/identifiers/scitt-identifiers.test.ts
index 964aca8..3398286 100644
--- a/src/scitt/identifiers/scitt-identifiers.test.ts
+++ b/src/scitt/identifiers/scitt-identifiers.test.ts
@@ -1,71 +1,51 @@
-import { base64url } from "jose";
-import { createHash } from 'crypto'
-import * as cbor from 'cbor-web'
 
 
-const urnPrefix = `urn:ietf:params:scitt`
-const nodeCryptoHashFunction = 'sha256'
-const mandatoryBaseEncoding = `base64url` // no pad .
+import cose from '../../../src'
 
-// https://www.iana.org/assignments/named-information/named-information.xhtml
-const nodeCryptoToIanaNamedHashFunctions = {
-  [nodeCryptoHashFunction]: 'sha-256'
-}
+let signedStatement: Buffer;
+let receipt: Buffer;
 
-// TODO:
-// Update to align with the TBS requirement in 
-// https://github.com/ietf-wg-scitt/draft-ietf-scitt-architecture/pull/145
+beforeAll(async () => {
+  const protectedHeader = new Map();
+  protectedHeader.set(1, -7)
+  const unprotectedHeader = new Map();
+  const signer = cose.lib.signer({
+    secretKeyJwk: {
+      kty: 'EC',
+      crv: 'P-256',
+      alg: 'ES256',
+      d: 'o_95vWSheg19YU7viU3PmW_kRIWk14HiVLXDXiZjEL0',
+      x: 'LYdh0ITBGLOUpywy0adFxXyaIaQapIEOLgfw7933TRE',
+      y: 'I6R3hgQZf2topOWa0VBjEugRgHISJ39LvOlfVX29P0w',
+    }
+  });
+  signedStatement = await signer.sign({ protectedHeader, unprotectedHeader, payload: Buffer.from('fake signed statement') });
+  receipt = await signer.sign({ protectedHeader, unprotectedHeader, payload: Buffer.from('fake receipt') });
+})
 
 describe('should produce a SCITT URN for SCITT Messages', () => {
+
   it('should produce a statement identifier', () => {
     // in SCITT, statements are opaque bytes of a known content type
     // for example some bytes of type application/json
-    const messageType = 'statement';
     const statement = JSON.stringify({ hello: ['world'] })
-    const statementHashBase64 = base64url.encode(createHash(nodeCryptoHashFunction).update(statement).digest());
-    const statementId = `${urnPrefix}:${messageType}:${nodeCryptoToIanaNamedHashFunctions[nodeCryptoHashFunction]}:${mandatoryBaseEncoding}:${statementHashBase64}`
+    const statementId = cose.scitt.identifiers.urn('statement', Buffer.from(statement))
     expect(statementId).toBe('urn:ietf:params:scitt:statement:sha-256:base64url:5i6UeRzg1SSUUjEUp73DdHUmHnh5uX0g97fHqnGmr1o')
   })
 
   it('should produce a signed statement identifier', () => {
     // in SCITT, signed statements are cose sign 1 bytes of type application/cose
-    // for the sake of this example, we substitute a simple cbor encoding for a cose sign 1.
-    const messageType = 'signed-statement';
-    const signedStatement = cbor.encode({ hello: ['world'] }) // normally this would be a valid cose sign 1 
-    // (including whatever mutable values are present in the unprotected header)
-    const signedStatementHashBase64 = base64url.encode(createHash(nodeCryptoHashFunction).update(signedStatement).digest());
-    const signedStatementId = `${urnPrefix}:${messageType}:${nodeCryptoToIanaNamedHashFunctions[nodeCryptoHashFunction]}:${mandatoryBaseEncoding}:${signedStatementHashBase64}`
-    expect(signedStatementId).toBe('urn:ietf:params:scitt:signed-statement:sha-256:base64url:h2drlVUvxYy5v9urLj7KGqBhGaaXS3Mf7K2P2us9d0U')
-    // note that when receipts are added to the unprotected header, the content identifier automatically changes to reflect their presence
-    // this also applies to all additional values added to the unprotected header before the identifier is computed.
-    // in this way, we may say that this identifier scheme is for a "transparent statement" of "unbounded transparency"
-    // we cannot know from the identifier itself, how many receipts will be present in the dereferenced content, but we do know
-    // the content type for the dereferenced bytes will always be application/cose.
+    const signedStatementId = cose.scitt.identifiers.urn('signed-statement', signedStatement)
+    // urn:ietf:params:scitt:signed-statement:sha-256:base64url:ysBmsRG2DagHYCgQuGHsG9alWWIiRwVRUhAz8j8cMxM
+    expect(signedStatementId.startsWith('urn:ietf:params:scitt:signed-statement:sha-256:base64url:')).toBe(true)
   })
 
   it('should produce a receipt identifier', () => {
     // in SCITT, receipts are cose sign 1 bytes of type application/cose
-    // for the sake of this example, we substitute a simple cbor encoding for a cose sign 1.
-    const messageType = 'receipt';
-    const receipt = cbor.encode({ hello: ['world'], other_identifiers: ['a', 'b'] }) // normally this would be a valid cose sign 1 
-    // (including whatever mutable values are present in the unprotected header)
-    const receiptHashBase64 = base64url.encode(createHash(nodeCryptoHashFunction).update(receipt).digest());
-    const receiptId = `${urnPrefix}:${messageType}:${nodeCryptoToIanaNamedHashFunctions[nodeCryptoHashFunction]}:${mandatoryBaseEncoding}:${receiptHashBase64}`
-    expect(receiptId).toBe('urn:ietf:params:scitt:receipt:sha-256:base64url:S10jY1p6CRl8Vu8tr_S5z4tpKdvhLf0AfkbA3c2o790')
-    // note that when additional proofs are added to the unprotected header, the content identifier automatically changes to reflect their presence
-    // this also applies to all additional values added to the unprotected header before the identifier is computed.
-
-    // this identifier is committing to the protected and unprotected header parameters, in addition to the signature
-    // this means if the receipt expires, the identifier expires
-    // this also means that if the receipt contains references to other identifiers, changing them will change its identifier.
-    // a common scenario we assume is that a receipt will refer to identifiers for other receipts
-    // this will build a DAG (directed acyclic graph), that is walkable assuming the following interface is implemented (regardless of API implementation details)
-
-    // receipt = dereference(receiptId)
-    // nodes = [receiptId] for each dereferencable receipt
-    // edges = [receiptId, nestedReceiptId] for each nested receipt
-
-    // because content identifiers are always computed from content, the content can never contain a reference to itself.
+    // in SCITT, signed statements are cose sign 1 bytes of type application/cose
+    const receiptId = cose.scitt.identifiers.urn('receipt', receipt)
+    // urn:ietf:params:scitt:receipt:sha-256:base64url:ysBmsRG2DagHYCgQuGHsG9alWWIiRwVRUhAz8j8cMxM
+    expect(receiptId.startsWith('urn:ietf:params:scitt:receipt:sha-256:base64url:')).toBe(true)
   })
 })
 
@@ -76,11 +56,10 @@ describe('should produce a URL from a SCITT URN', () => {
     // given some bytes and a content type
     // the SCITT data URL is the trivial data URL of the form
     const contentType = `application/cose`
-    const receipt = cbor.encode({ hello: ['world'], other_identifiers: ['a', 'b'] }) // normally this would be a valid cose sign 1
     const baseEncodedReceipt = Buffer.from(receipt).toString('base64')
     const dataURL = `data:${contentType};base64,${baseEncodedReceipt}`;
     // note that base64 is not the same as base64url no pad.
-    expect(dataURL).toBe('data:application/cose;base64,omVoZWxsb4Fld29ybGRxb3RoZXJfaWRlbnRpZmllcnOCYWFhYg==')
+    expect(dataURL.startsWith('data:application/cose;base64,')).toBe(true)
   })
   it('SCITT SCRAPI URLs', () => {
     // SCRAPI provides an optional to implement HTTP API that supports the required dereference operation necessary to compute the dag
@@ -102,7 +81,3 @@ describe('should produce a URL from a SCITT URN', () => {
   })
 })
 
-// SCITT does not require Text Encoded Identifiers (URLs or URNs)
-// Binary Encoded Identifiers for URLs or URNs
-// MAY be constructed according to __RFC__.
-// SCRAPI does not define http interfaces for working with binary identifiers.
diff --git a/src/scitt/identifiers/urn.ts b/src/scitt/identifiers/urn.ts
new file mode 100644
index 0000000..360473f
--- /dev/null
+++ b/src/scitt/identifiers/urn.ts
@@ -0,0 +1,27 @@
+
+import { base64url } from "jose";
+import { createHash } from 'crypto'
+
+import cose from '../../../src'
+
+const urnPrefix = `urn:ietf:params:scitt`
+const nodeCryptoHashFunction = 'sha256'
+const mandatoryBaseEncoding = `base64url` // no pad .
+
+// https://www.iana.org/assignments/named-information/named-information.xhtml
+const nodeCryptoToIanaNamedHashFunctions = {
+  [nodeCryptoHashFunction]: 'sha-256'
+}
+
+export const urn = (type: string, message: Buffer) => {
+  if (['statement', 'transparent-statement'].includes(type)) {
+    const messageHashBase64 = base64url.encode(createHash(nodeCryptoHashFunction).update(message).digest());
+    const scittUrn = `${urnPrefix}:${type}:${nodeCryptoToIanaNamedHashFunctions[nodeCryptoHashFunction]}:${mandatoryBaseEncoding}:${messageHashBase64}`
+    return scittUrn;
+  } else {
+    const tbs = cose.extractTBS(message)
+    const messageHashBase64 = base64url.encode(createHash(nodeCryptoHashFunction).update(tbs).digest());
+    const scittUrn = `${urnPrefix}:${type}:${nodeCryptoToIanaNamedHashFunctions[nodeCryptoHashFunction]}:${mandatoryBaseEncoding}:${messageHashBase64}`
+    return scittUrn
+  }
+}
\ No newline at end of file
diff --git a/src/scitt/index.ts b/src/scitt/index.ts
index 0c0b983..bc7bbd2 100644
--- a/src/scitt/index.ts
+++ b/src/scitt/index.ts
@@ -1,4 +1,4 @@
 import * as statement from './statement'
 import * as receipt from './receipt'
-
-export { statement, receipt }
\ No newline at end of file
+import * as identifiers from './identifiers'
+export { statement, receipt, identifiers }
\ No newline at end of file