Remove the SignedTransaction.id field, which took part in serialisation. Calculate it on demand instead.

core/src/main/kotlin/net/corda/core/transactions/SignedTransaction.kt

@@ -23,8 +23,7 @@ import java.util.*
  * A transaction ID should be the hash of the [WireTransaction] Merkle tree root. Thus adding or removing a signature does not change it.
  */
 data class SignedTransaction(val txBits: SerializedBytes<WireTransaction>,
-                             val sigs: List<DigitalSignature.WithKey>,
+                             val sigs: List<DigitalSignature.WithKey>
-                             override val id: SecureHash
 ) : NamedByHash {
     init {
         require(sigs.isNotEmpty())
@@ -33,11 +32,14 @@ data class SignedTransaction(val txBits: SerializedBytes<WireTransaction>,
     // TODO: This needs to be reworked to ensure that the inner WireTransaction is only ever deserialised sandboxed.
 
     /** Lazily calculated access to the deserialised/hashed transaction data. */
-    val tx: WireTransaction by lazy {
+    val tx: WireTransaction by lazy { WireTransaction.deserialize(txBits) }
-        val temp = WireTransaction.deserialize(txBits)
+
-        check(temp.id == id) { "Supplied transaction ID does not match deserialized transaction's ID - this is probably a problem in serialization/deserialization" }
+    /**
-        temp
+     * The Merkle root of the inner [WireTransaction]. Note that this is _not_ the same as the simple hash of
-    }
+     * [txBits], which would not use the Merkle tree structure. If the difference isn't clear, please consult
+     * the user guide section "Transaction tear-offs" to learn more about Merkle trees.
+     */
+    override val id: SecureHash get() = tx.id
 
     class SignaturesMissingException(val missing: Set<CompositeKey>, val descriptions: List<String>, override val id: SecureHash) : NamedByHash, SignatureException() {
         override fun toString(): String {

core/src/main/kotlin/net/corda/core/transactions/TransactionBuilder.kt

@@ -137,7 +137,7 @@ open class TransactionBuilder(
                 throw IllegalStateException("Missing signatures on the transaction for the public keys: ${missing.joinToString()}")
         }
         val wtx = toWireTransaction()
-        return SignedTransaction(wtx.serialize(), ArrayList(currentSigs), wtx.id)
+        return SignedTransaction(wtx.serialize(), ArrayList(currentSigs))
     }
 
     open fun addInputState(stateAndRef: StateAndRef<*>) {

core/src/test/kotlin/net/corda/core/contracts/TransactionTests.kt

@@ -35,7 +35,7 @@ class TransactionTests {
                 timestamp = null
         )
         val bytes: SerializedBytes<WireTransaction> = wtx.serialized
-        fun make(vararg keys: KeyPair) = SignedTransaction(bytes, keys.map { it.signWithECDSA(wtx.id.bytes) }, wtx.id)
+        fun make(vararg keys: KeyPair) = SignedTransaction(bytes, keys.map { it.signWithECDSA(wtx.id.bytes) })
         assertFailsWith<IllegalArgumentException> { make().verifySignatures() }
 
         assertEquals(

finance/src/main/kotlin/net/corda/contracts/testing/Generators.kt

@@ -84,8 +84,7 @@ class SignedTransactionGenerator : Generator<SignedTransaction>(SignedTransactio
         val wireTransaction = WiredTransactionGenerator().generate(random, status)
         return SignedTransaction(
                 txBits = wireTransaction.serialized,
-                sigs = listOf(NullSignature),
+                sigs = listOf(NullSignature)
-                id = wireTransaction.id
         )
     }
 }

node/src/test/kotlin/net/corda/node/services/database/RequeryConfigurationTest.kt

@@ -167,6 +167,6 @@ class RequeryConfigurationTest {
                 type = TransactionType.General(),
                 timestamp = null
         )
-        return SignedTransaction(wtx.serialized, listOf(DigitalSignature.WithKey(NullPublicKey, ByteArray(1))), wtx.id)
+        return SignedTransaction(wtx.serialized, listOf(DigitalSignature.WithKey(NullPublicKey, ByteArray(1))))
     }
 }

node/src/test/kotlin/net/corda/node/services/persistence/DBTransactionStorageTests.kt

@@ -156,6 +156,6 @@ class DBTransactionStorageTests {
                 type = TransactionType.General(),
                 timestamp = null
         )
-        return SignedTransaction(wtx.serialized, listOf(DigitalSignature.WithKey(NullPublicKey, ByteArray(1))), wtx.id)
+        return SignedTransaction(wtx.serialized, listOf(DigitalSignature.WithKey(NullPublicKey, ByteArray(1))))
     }
 }

test-utils/src/main/kotlin/net/corda/testing/TestDSL.kt

@@ -282,7 +282,7 @@ data class TestLedgerDSLInterpreter private constructor (
     override fun verifies(): EnforceVerifyOrFail {
         try {
             val usedInputs = mutableSetOf<StateRef>()
-            services.recordTransactions(transactionsUnverified.map { SignedTransaction(it.serialized, listOf(NullSignature), it.id) })
+            services.recordTransactions(transactionsUnverified.map { SignedTransaction(it.serialized, listOf(NullSignature)) })
             for ((key, value) in transactionWithLocations) {
                 val wtx = value.transaction
                 val ltx = wtx.toLedgerTransaction(services)
@@ -294,7 +294,7 @@ data class TestLedgerDSLInterpreter private constructor (
                     throw DoubleSpentInputs(txIds)
                 }
                 usedInputs.addAll(wtx.inputs)
-                services.recordTransactions(SignedTransaction(wtx.serialized, listOf(NullSignature), wtx.id))
+                services.recordTransactions(SignedTransaction(wtx.serialized, listOf(NullSignature)))
             }
             return EnforceVerifyOrFail.Token
         } catch (exception: TransactionVerificationException) {
@@ -340,7 +340,7 @@ fun signAll(transactionsToSign: List<WireTransaction>, extraKeys: List<KeyPair>)
         val key = keyLookup[it] ?: throw IllegalArgumentException("Missing required key for ${it.toStringShort()}")
         signatures += key.signWithECDSA(wtx.id)
     }
-    SignedTransaction(bits, signatures, wtx.id)
+    SignedTransaction(bits, signatures)
 }
 
 /**