Updated on 2026-08-14

tangem-core/src/main/java/com/tangem/commands/ReadIssuerExtraDataCommand.kt

@@ -62,7 +62,7 @@ class ReadIssuerExtraDataCommand(
         val tlvBuilder = TlvBuilder()
         tlvBuilder.append(TlvTag.Pin, cardEnvironment.pin1)
         tlvBuilder.append(TlvTag.CardId, cardEnvironment.cardId)
-        tlvBuilder.append(TlvTag.Mode, IssuerDataMode.ExtraData)
+        tlvBuilder.append(TlvTag.Mode, EXTRA_DATA_MODE)
         tlvBuilder.append(TlvTag.Offset, offset)
         return CommandApdu(Instruction.ReadIssuerData, tlvBuilder.serialize())
     }
@@ -83,4 +83,12 @@ class ReadIssuerExtraDataCommand(
             throw TaskError.SerializeCommandError()
         }
     }
+
+    companion object {
+        /**
+         * This mode value specifies that this command retrieves Issuer EXTRA data from the card
+         * (with value 0 the command will get instead simple Issuer Data from the card).
+         */
+        const val EXTRA_DATA_MODE = 1
+    }
 }

tangem-core/src/main/java/com/tangem/commands/WriteIssuerExtraDataCommand.kt

@@ -9,9 +9,24 @@ import com.tangem.common.tlv.TlvMapper
 import com.tangem.common.tlv.TlvTag
 import com.tangem.tasks.TaskError
 
+/**
+ * This enum specifies modes for [WriteIssuerExtraDataCommand].
+ */
 enum class IssuerDataMode(val code: Byte) {
-    ExtraData(1),
+    /**
+     * This mode is required to initiate writing issuer extra data to the card.
+     */
+    InitializeWritingExtraData(1),
+    /**
+     * With this mode, the command writes part of issuer extra data
+     * (block of a size [WriteIssuerExtraDataCommand.SINGLE_WRITE_SIZE]) to the card.
+     */
     WriteExtraData(2),
+    /**
+     * This mode is used after the issuer extra data was fully written to the card.
+     * Under this mode the command provides the issuer signature
+     * to confirm the validity of data that was written to card.
+     */
     FinalizeExtraData(3);
 
     companion object {
@@ -44,7 +59,7 @@ class WriteIssuerExtraDataCommand(
         verifier: IssuerDataVerifier = DefaultIssuerDataVerifier()
 ) : CommandSerializer<WriteIssuerDataResponse>(), IssuerDataVerifier by verifier {
 
-    var mode: IssuerDataMode = IssuerDataMode.ExtraData
+    var mode: IssuerDataMode = IssuerDataMode.InitializeWritingExtraData
     var offset: Int = 0
 
     override fun serialize(cardEnvironment: CardEnvironment): CommandApdu {
@@ -55,7 +70,7 @@ class WriteIssuerExtraDataCommand(
         tlvBuilder.append(TlvTag.Mode, mode)
 
         when (mode) {
-            IssuerDataMode.ExtraData -> {
+            IssuerDataMode.InitializeWritingExtraData -> {
                 tlvBuilder.append(TlvTag.Size, issuerData.size)
                 tlvBuilder.append(TlvTag.IssuerDataSignature, startingSignature)
                 tlvBuilder.append(TlvTag.IssuerDataCounter, issuerDataCounter)

tangem-core/src/main/java/com/tangem/tasks/WriteIssuerExtraDataTask.kt

@@ -59,7 +59,7 @@ internal class WriteIssuerExtraDataTask(
 
                 is CompletionResult.Success -> {
                     when (command.mode) {
-                        IssuerDataMode.ExtraData -> {
+                        IssuerDataMode.InitializeWritingExtraData -> {
                             command.mode = IssuerDataMode.WriteExtraData
                             writeIssuerData(command, callback)
                             return@sendCommand