diff --git a/src/services/index.ts b/src/services/index.ts
index 79b5128..b8d275a 100644
--- a/src/services/index.ts
+++ b/src/services/index.ts
@@ -1 +1,2 @@
 export * from './cache'
+export * from './signer'
diff --git a/src/services/signer/index.ts b/src/services/signer/index.ts
new file mode 100644
index 0000000..8851028
--- /dev/null
+++ b/src/services/signer/index.ts
@@ -0,0 +1,143 @@
+import { toast } from 'react-toastify'
+import { Meta, SignedEventContent } from '../../types'
+import {
+  parseCreateSignatureEventContent,
+  parseNostrEvent,
+  SigitStatus,
+  SignStatus
+} from '../../utils'
+import { MetaParseError } from '../../types/errors/MetaParseError'
+import { verifyEvent } from 'nostr-tools'
+import { appPrivateRoutes, appPublicRoutes } from '../../routes'
+
+export class SignerService {
+  #signers: `npub1${string}`[] = []
+  #nextSigner: `npub1${string}` | undefined
+  #signatures = new Map<`npub1${string}`, string>()
+  #signersStatus = new Map<`npub1${string}`, SignStatus>()
+  #lastSignerSig: string | undefined
+  constructor(source: Meta) {
+    this.#process(source.createSignature, source.docSignatures)
+  }
+
+  getNextSigner = () => {
+    return this.#nextSigner
+  }
+
+  isNextSigner = (npub: `npub1${string}`) => {
+    return this.#nextSigner === npub
+  }
+
+  isLastSigner = (npub: `npub1${string}`) => {
+    const lastIndex = this.#signers.length - 1
+    const npubIndex = this.#signers.indexOf(npub)
+    return npubIndex === lastIndex
+  }
+
+  #isFullySigned = () => {
+    const signedBy = Object.keys(this.#signatures) as `npub1${string}`[]
+    const isCompletelySigned = this.#signers.every((signer) =>
+      signedBy.includes(signer)
+    )
+    return isCompletelySigned
+  }
+
+  getSignedStatus = () => {
+    return this.#isFullySigned() ? SigitStatus.Complete : SigitStatus.Partial
+  }
+
+  getSignerStatus = (npub: `npub1${string}`) => {
+    return this.#signersStatus.get(npub)
+  }
+
+  getNavigate = (npub: `npub1${string}`) => {
+    return this.isNextSigner(npub)
+      ? appPrivateRoutes.sign
+      : appPublicRoutes.verify
+  }
+
+  getLastSignerSig = () => {
+    return this.#lastSignerSig
+  }
+
+  #process = (
+    createSignature: string,
+    docSignatures: { [key: `npub1${string}`]: string }
+  ) => {
+    try {
+      const createSignatureEvent = parseNostrEvent(createSignature)
+      const { signers } = parseCreateSignatureEventContent(
+        createSignatureEvent.content
+      )
+      const getPrevSignerSig = (npub: `npub1${string}`) => {
+        if (signers[0] === npub) {
+          return createSignatureEvent.sig
+        }
+
+        // Find the index of signer
+        const currentSignerIndex = signers.findIndex(
+          (signer) => signer === npub
+        )
+
+        // Return if could not found user in signer's list
+        if (currentSignerIndex === -1) return
+
+        // Find prev signer
+        const prevSigner = signers[currentSignerIndex - 1]
+
+        // Get the signature of prev signer
+        return this.#signatures.get(prevSigner)
+      }
+
+      this.#signers = [...signers]
+      for (const npub in docSignatures) {
+        try {
+          // Parse each signature event
+          const event = parseNostrEvent(docSignatures[npub as `npub1${string}`])
+          this.#signatures.set(npub as `npub1${string}`, event.sig)
+          const isValidSignature = verifyEvent(event)
+          if (isValidSignature) {
+            const prevSignersSig = getPrevSignerSig(npub as `npub1${string}`)
+            const signedEvent: SignedEventContent = JSON.parse(event.content)
+            if (
+              signedEvent.prevSig &&
+              prevSignersSig &&
+              signedEvent.prevSig === prevSignersSig
+            ) {
+              this.#signersStatus.set(
+                npub as `npub1${string}`,
+                SignStatus.Signed
+              )
+              this.#lastSignerSig = event.sig
+            }
+          } else {
+            this.#signersStatus.set(
+              npub as `npub1${string}`,
+              SignStatus.Invalid
+            )
+          }
+        } catch (error) {
+          this.#signersStatus.set(npub as `npub1${string}`, SignStatus.Invalid)
+        }
+      }
+
+      this.#signers
+        .filter((s) => !this.#signatures.has(s))
+        .forEach((s) => this.#signersStatus.set(s, SignStatus.Pending))
+
+      // Get the first signer that hasn't signed
+      const nextSigner = this.#signers.find((s) => !this.#signatures.has(s))
+      if (nextSigner) {
+        this.#nextSigner = nextSigner
+        this.#signersStatus.set(nextSigner, SignStatus.Awaiting)
+      }
+    } catch (error) {
+      if (error instanceof MetaParseError) {
+        toast.error(error.message)
+        console.error(error.name, error.message, error.cause, error.context)
+      } else {
+        console.error('Unexpected error', error)
+      }
+    }
+  }
+}