diff --git a/mirai-core-timpc/src/commonMain/kotlin/net.mamoe.mirai.timpc/network/packet/login/PasswordSubmission.kt b/mirai-core-timpc/src/commonMain/kotlin/net.mamoe.mirai.timpc/network/packet/login/PasswordSubmission.kt
index c6ea1822d..e635ae10d 100644
--- a/mirai-core-timpc/src/commonMain/kotlin/net.mamoe.mirai.timpc/network/packet/login/PasswordSubmission.kt
+++ b/mirai-core-timpc/src/commonMain/kotlin/net.mamoe.mirai.timpc/network/packet/login/PasswordSubmission.kt
@@ -27,7 +27,7 @@ internal inline class PrivateKey(override val value: ByteArray) : DecrypterByteA
 
 internal inline class SubmitPasswordResponseDecrypter(private val privateKey: PrivateKey) : Decrypter {
     override fun decrypt(input: ByteReadPacket, offset: Int, length: Int): ByteReadPacket {
-        var decrypted = ShareKey.decrypt(input)
+        var decrypted = ShareKey.decrypt(input, offset, length)
         (decrypted.remaining).let {
             if (it.toInt() % 8 == 0 && it >= 16) {
                 decrypted = try {
@@ -263,7 +263,7 @@ internal object SubmitPasswordPacket : PacketFactory<SubmitPasswordPacket.LoginR
 }
 
 internal inline class SessionResponseDecryptionKey(private val delegate: IoBuffer) : Decrypter {
-    override fun decrypt(input: ByteReadPacket, offset: Int, length: Int): ByteReadPacket = input.decryptBy(delegate)
+    override fun decrypt(input: ByteReadPacket, offset: Int, length: Int): ByteReadPacket = input.decryptBy(delegate, offset, length)
 
     override fun toString(): String = "SessionResponseDecryptionKey"
 
diff --git a/mirai-core-timpc/src/jvmTest/kotlin/PacketDebugger.kt b/mirai-core-timpc/src/jvmTest/kotlin/PacketDebugger.kt
index 823b491ec..85097b2c4 100644
--- a/mirai-core-timpc/src/jvmTest/kotlin/PacketDebugger.kt
+++ b/mirai-core-timpc/src/jvmTest/kotlin/PacketDebugger.kt
@@ -24,10 +24,7 @@ import net.mamoe.mirai.timpc.network.packet.login.CaptchaKey
 import net.mamoe.mirai.timpc.network.packet.login.HeartbeatPacket
 import net.mamoe.mirai.timpc.network.packet.login.ShareKey
 import net.mamoe.mirai.timpc.network.packet.login.TouchKey
-import net.mamoe.mirai.utils.cryptor.Decrypter
-import net.mamoe.mirai.utils.cryptor.DecryptionFailedException
-import net.mamoe.mirai.utils.cryptor.NoDecrypter
-import net.mamoe.mirai.utils.cryptor.decryptBy
+import net.mamoe.mirai.utils.cryptor.*
 import net.mamoe.mirai.utils.io.*
 import org.pcap4j.core.BpfProgram.BpfCompileMode
 import org.pcap4j.core.PacketListener
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/Decrypters.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/Decrypters.kt
index 630c7b5dc..666fd6450 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/Decrypters.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/Decrypters.kt
@@ -45,11 +45,14 @@ object NoDecrypter : Decrypter, DecrypterType<NoDecrypter> {
     }
 }
 
+fun Decrypter.decrypt(input: ByteReadPacket): ByteReadPacket = this.decrypt(input, 0, input.remaining.toInt())
+
 /**
  * 解密器
  */
 interface Decrypter {
-    fun decrypt(input: ByteReadPacket, offset: Int = 0, length: Int = (input.remaining - offset).toInt()): ByteReadPacket
+    // do not write with default args. NoSuchMethodError when inline classes override this function
+    fun decrypt(input: ByteReadPacket, offset: Int, length: Int): ByteReadPacket
     /**
      * 连接后将会先用 this 解密, 再用 [another] 解密
      */
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/TEA.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/TEA.kt
index c08ef64c0..b921fcfbf 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/TEA.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/cryptor/TEA.kt
@@ -94,21 +94,19 @@ fun IoBuffer.decryptBy(key: ByteArray, offset: Int = 0, length: Int = readRemain
 
 // region ByteReadPacket extension
 
-fun ByteReadPacket.decryptBy(key: ByteArray, offset: Int = 0, length: Int = key.size - offset): ByteReadPacket = decryptAsByteArray(key) { data -> ByteReadPacket(data, offset, length) }
+fun ByteReadPacket.decryptBy(key: ByteArray, offset: Int = 0, length: Int = key.size - offset): ByteReadPacket = decryptAsByteArray(key, offset, length) { data -> ByteReadPacket(data) }
 
-fun ByteReadPacket.decryptBy(key: IoBuffer, offset: Int = 0, length: Int = key.readRemaining - offset): ByteReadPacket = decryptAsByteArray(key) { data -> ByteReadPacket(data,  offset, length) }
+fun ByteReadPacket.decryptBy(key: IoBuffer, offset: Int = 0, length: Int = key.readRemaining - offset): ByteReadPacket = decryptAsByteArray(key, offset, length) { data -> ByteReadPacket(data) }
 
-inline fun <R> ByteReadPacket.decryptAsByteArray(key: ByteArray, consumer: (ByteArray) -> R): R =
+inline fun <R> ByteReadPacket.decryptAsByteArray(key: ByteArray, offset: Int = 0, length: Int = key.size - offset, consumer: (ByteArray) -> R): R =
     ByteArrayPool.useInstance {
-        val length = remaining.toInt()
-        readFully(it, 0, length)
+        readFully(it, offset, length)
         consumer(it.decryptBy(key, length))
     }.also { close() }
 
-inline fun <R> ByteReadPacket.decryptAsByteArray(key: IoBuffer, consumer: (ByteArray) -> R): R =
+inline fun <R> ByteReadPacket.decryptAsByteArray(key: IoBuffer, offset: Int = 0, length: Int = key.readRemaining - offset, consumer: (ByteArray) -> R): R =
     ByteArrayPool.useInstance {
-        val length = remaining.toInt()
-        readFully(it, 0, length)
+        readFully(it, offset, length)
         consumer(it.decryptBy(key, length))
     }.also { close() }
 
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/io/OutputUtils.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/io/OutputUtils.kt
index 091b9e543..2704b7a3e 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/io/OutputUtils.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/utils/io/OutputUtils.kt
@@ -47,7 +47,7 @@ fun BytePacketBuilder.writeShortLVByteArray(byteArray: ByteArray): Int {
 inline fun BytePacketBuilder.writeIntLVPacket(tag: UByte? = null, lengthOffset: ((Long) -> Long) = {it}, builder: BytePacketBuilder.() -> Unit): Int =
     BytePacketBuilder().apply(builder).build().use {
         if (tag != null) writeUByte(tag)
-        val length = (lengthOffset.invoke(it.remaining) ?: it.remaining).coerceAtMostOrFail(0xFFFFL)
+        val length = lengthOffset.invoke(it.remaining).coerceAtMostOrFail(0xFFFFL)
         writeInt(length.toInt())
         writePacket(it)
         return length.toInt()
@@ -56,7 +56,7 @@ inline fun BytePacketBuilder.writeIntLVPacket(tag: UByte? = null, lengthOffset:
 inline fun BytePacketBuilder.writeShortLVPacket(tag: UByte? = null, lengthOffset: ((Long) -> Long) = {it}, builder: BytePacketBuilder.() -> Unit): Int =
     BytePacketBuilder().apply(builder).build().use {
         if (tag != null) writeUByte(tag)
-        val length = (lengthOffset.invoke(it.remaining) ?: it.remaining).coerceAtMostOrFail(0xFFFFL)
+        val length = lengthOffset.invoke(it.remaining).coerceAtMostOrFail(0xFFFFL)
         writeUShort(length.toUShort())
         writePacket(it)
         return length.toInt()
@@ -65,7 +65,7 @@ inline fun BytePacketBuilder.writeShortLVPacket(tag: UByte? = null, lengthOffset
 inline fun BytePacketBuilder.writeUVarIntLVPacket(tag: UByte? = null, lengthOffset: ((Long) -> Long) = {it}, builder: BytePacketBuilder.() -> Unit) =
     BytePacketBuilder().apply(builder).build().use {
         if (tag != null) writeUByte(tag)
-        writeUVarInt((lengthOffset.invoke(it.remaining) ?: it.remaining).coerceAtMostOrFail(0xFFFFL))
+        writeUVarInt(lengthOffset.invoke(it.remaining).coerceAtMostOrFail(0xFFFFL))
         writePacket(it)
     }