diff --git a/mirai-core/src/commonMain/kotlin/MiraiImpl.kt b/mirai-core/src/commonMain/kotlin/MiraiImpl.kt
index 27b76e3b8..895f9a812 100644
--- a/mirai-core/src/commonMain/kotlin/MiraiImpl.kt
+++ b/mirai-core/src/commonMain/kotlin/MiraiImpl.kt
@@ -16,7 +16,6 @@ import io.ktor.client.request.*
 import io.ktor.client.request.forms.*
 import io.ktor.http.*
 import io.ktor.utils.io.core.*
-import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.io.core.discardExact
 import kotlinx.io.core.readBytes
@@ -577,7 +576,7 @@ internal open class MiraiImpl : IMirai, LowLevelApiAccessor {
             val rep = network.run {
                 Mirai.Http.get<String> {
                     url("https://qqweb.qq.com/c/activedata/get_mygroup_data")
-                    parameter("bkn", bkn)
+                    parameter("bkn", client.wLoginSigInfo.bkn)
                     parameter("gc", groupId)
                     if (page != -1) {
                         parameter("page", page)
@@ -795,7 +794,7 @@ internal open class MiraiImpl : IMirai, LowLevelApiAccessor {
                 append("group_code", groupId)
                 append("seconds", seconds)
                 append("anony_nick", anonymousNick)
-                append("bkn", bot.bkn)
+                append("bkn", bot.client.wLoginSigInfo.bkn)
             })
             headers {
                 append(
diff --git a/mirai-core/src/commonMain/kotlin/QQAndroidBot.kt b/mirai-core/src/commonMain/kotlin/QQAndroidBot.kt
index 65f1defce..eeb8f2feb 100644
--- a/mirai-core/src/commonMain/kotlin/QQAndroidBot.kt
+++ b/mirai-core/src/commonMain/kotlin/QQAndroidBot.kt
@@ -37,9 +37,9 @@ import net.mamoe.mirai.internal.network.handler.state.StateObserver
 import net.mamoe.mirai.internal.network.handler.state.safe
 import net.mamoe.mirai.internal.network.impl.netty.ForceOfflineException
 import net.mamoe.mirai.internal.network.impl.netty.NettyNetworkHandlerFactory
-import net.mamoe.mirai.internal.network.protocol.packet.login.StatSvc
 import net.mamoe.mirai.internal.network.notice.*
 import net.mamoe.mirai.internal.network.notice.decoders.MsgInfoDecoder
+import net.mamoe.mirai.internal.network.protocol.packet.login.StatSvc
 import net.mamoe.mirai.internal.utils.subLogger
 import net.mamoe.mirai.utils.BotConfiguration
 import net.mamoe.mirai.utils.MiraiLogger
@@ -240,14 +240,6 @@ internal open class QQAndroidBot constructor(
             },
         ) // We can move the factory to configuration but this is not necessary for now.
     }
-
-    /**
-     * 获取 获取群公告 所需的 bkn 参数
-     * */ // TODO: 2021/4/26 extract it after #1141 merged
-    val bkn: Int
-        get() = client.wLoginSigInfo.sKey.data
-            .fold(5381) { acc: Int, b: Byte -> acc + acc.shl(5) + b.toInt() }
-            .and(Int.MAX_VALUE)
 }
 
 internal fun QQAndroidBot.getGroupByUinOrFail(uin: Long) =
diff --git a/mirai-core/src/commonMain/kotlin/contact/announcement/AnnouncementsImpl.kt b/mirai-core/src/commonMain/kotlin/contact/announcement/AnnouncementsImpl.kt
index 323f9817a..6a1ec7ef3 100644
--- a/mirai-core/src/commonMain/kotlin/contact/announcement/AnnouncementsImpl.kt
+++ b/mirai-core/src/commonMain/kotlin/contact/announcement/AnnouncementsImpl.kt
@@ -28,10 +28,6 @@ import net.mamoe.mirai.internal.QQAndroidBot
 import net.mamoe.mirai.internal.asQQAndroidBot
 import net.mamoe.mirai.internal.contact.GroupImpl
 import net.mamoe.mirai.internal.contact.OnlineAnnouncementImpl
-import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.deleteGroupAnnouncement
-import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.getGroupAnnouncement
-import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.getRawGroupAnnouncements
-import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.sendGroupAnnouncement
 import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.toAnnouncement
 import net.mamoe.mirai.internal.contact.announcement.AnnouncementProtocol.toGroupAnnouncement
 import net.mamoe.mirai.internal.network.highway.ChannelKind
@@ -41,8 +37,6 @@ import net.mamoe.mirai.internal.network.psKey
 import net.mamoe.mirai.internal.network.sKey
 import net.mamoe.mirai.internal.utils.io.writeResource
 import net.mamoe.mirai.utils.*
-import net.mamoe.mirai.utils.Either.Companion.onLeft
-import net.mamoe.mirai.utils.Either.Companion.rightOrNull
 import java.util.stream.Stream
 
 internal class AnnouncementsImpl(
@@ -169,7 +163,7 @@ internal object AnnouncementProtocol {
         val resp = Mirai.Http.post<String> {
             url("https://web.qun.qq.com/cgi-bin/announce/upload_img")
             body = MultiPartFormDataContent(formData {
-                append("\"bkn\"", bkn)
+                append("\"bkn\"", client.wLoginSigInfo.bkn)
                 append("\"source\"", "troopNotice")
                 append("m", "0")
                 append(
@@ -212,7 +206,7 @@ internal object AnnouncementProtocol {
             )
             body = MultiPartFormDataContent(formData {
                 append("qid", groupId)
-                this.append("bkn", bkn)
+                append("bkn", client.wLoginSigInfo.bkn)
                 append("text", announcement.msg.text)
                 append("pinned", announcement.pinned)
                 image?.let {
@@ -243,7 +237,7 @@ internal object AnnouncementProtocol {
             url("https://web.qun.qq.com/cgi-bin/announce/list_announce")
             body = MultiPartFormDataContent(formData {
                 append("qid", groupId)
-                append("bkn", bkn)
+                append("bkn", client.wLoginSigInfo.bkn)
                 append("ft", 23)  //好像是一个用来识别应用的参数
                 append("s", if (page == 1) 0 else -(page * amount + 1))  // 第一页这里的参数应该是-1
                 append("n", amount)
@@ -288,7 +282,7 @@ internal object AnnouncementProtocol {
         fid: String
     ) = MultiPartFormDataContent(formData {
         append("qid", groupId)
-        append("bkn", bkn)
+        append("bkn", client.wLoginSigInfo.bkn)
         append("fid", fid)
         append("format", "json")
     })
diff --git a/mirai-core/src/commonMain/kotlin/network/keys.kt b/mirai-core/src/commonMain/kotlin/network/keys.kt
index 8ca5a7808..24acd7f7d 100644
--- a/mirai-core/src/commonMain/kotlin/network/keys.kt
+++ b/mirai-core/src/commonMain/kotlin/network/keys.kt
@@ -127,6 +127,14 @@ internal data class WLoginSigInfo(
     var encryptedDownloadSession: EncryptedDownloadSession? = null,
 ) {
 
+    /**
+     * 获取 获取群公告 所需的 bkn 参数
+     * */
+    val bkn: Int
+        get() = sKey.data
+            .fold(5381) { acc: Int, b: Byte -> acc + acc.shl(5) + b.toInt() }
+            .and(Int.MAX_VALUE)
+
     //图片加密下载
     //是否加密从bigdatachannel处得知
     @Serializable