test: create fake TSS library for testing (#15908)

Signed-off-by: Miroslav Gatsanoga <miroslav.gatsanoga@limechain.tech>
Co-authored-by: Neeharika Sompalli <52669918+Neeharika-Sompalli@users.noreply.github.com>

hedera-node/hedera-app/src/main/java/com/hedera/node/app/tss/api/TssLibrary.java

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+/*
+ * Copyright (C) 2024 Hedera Hashgraph, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hedera.node.app.tss.api;
+
+import com.hedera.node.app.tss.pairings.PairingPrivateKey;
+import com.hedera.node.app.tss.pairings.PairingPublicKey;
+import com.hedera.node.app.tss.pairings.PairingSignature;
+import edu.umd.cs.findbugs.annotations.NonNull;
+import java.util.List;
+
+/**
+ * A Threshold Signature Scheme Library.
+ * Contract of TSS:
+ * <ul>
+ *     <li>Generate TssMessages out of PrivateShares</li>
+ *     <li>Verify TssMessages out of a ParticipantDirectory</li>
+ *     <li>Obtain PrivateShares out of TssMessages for each owned share</li>
+ *     <li>Aggregate PrivateShares</li>
+ *     <li>Obtain PublicShares out of TssMessages for each share</li>
+ *     <li>Aggregate PublicShares</li>
+ *     <li>Sign Messages</li>
+ *     <li>Verify Signatures</li>
+ *     <li>Aggregate Signatures</li>
+ * </ul>
+ */
+public interface TssLibrary {
+
+    /**
+     * Generate a {@link TssMessage} for a {@code tssParticipantDirectory}, from a random private share.
+     * This method can be used to bootstrap the protocol as it does not need the existence of a previous {@link
+     * TssPrivateShare}
+     *
+     * @param tssParticipantDirectory the participant directory that we should generate the message for
+     * @return a {@link TssMessage} produced out of a random share.
+     */
+    @NonNull
+    TssMessage generateTssMessage(@NonNull TssParticipantDirectory tssParticipantDirectory);
+
+    /**
+     * Generate a {@link TssMessage} for a {@code tssParticipantDirectory}, for the specified {@link
+     * TssPrivateShare}.
+     *
+     * @param tssParticipantDirectory the participant directory that we should generate the message for
+     * @param privateShare       the secret to use for generating new keys
+     * @return a TssMessage for the requested share.
+     */
+    @NonNull
+    TssMessage generateTssMessage(
+            @NonNull TssParticipantDirectory tssParticipantDirectory, @NonNull TssPrivateShare privateShare);
+
+    /**
+     * Verify that a {@link TssMessage} is valid.
+     *
+     * @param participantDirectory the participant directory used to generate the message
+     * @param tssMessage the {@link TssMessage} to validate
+     * @return true if the message is valid, false otherwise
+     */
+    boolean verifyTssMessage(@NonNull TssParticipantDirectory participantDirectory, @NonNull TssMessage tssMessage);
+
+    /**
+     * Compute all private shares that belongs to this participant from a threshold minimum number of {@link
+     * TssMessage}s.
+     * It is the responsibility of the caller to ensure that the list of validTssMessages meets the required
+     * threshold.
+     *
+     * @param participantDirectory the pending participant directory that we should generate the private share for
+     * @param validTssMessages the TSS messages to extract the private shares from. They must be previously
+     * validated.
+     * @return a sorted by sharedId list of private shares the current participant owns.
+     * @throws IllegalStateException if there aren't enough messages to meet the threshold
+     */
+    @NonNull
+    List<TssPrivateShare> decryptPrivateShares(
+            @NonNull TssParticipantDirectory participantDirectory, @NonNull List<TssMessage> validTssMessages);
+
+    /**
+     * Aggregate a threshold number of {@link TssPrivateShare}s.
+     *
+     * @param privateShares the private shares to aggregate
+     * @return the aggregate private key
+     * @throws IllegalStateException the list of private shares does not meet the required threshold.
+     */
+    @NonNull
+    PairingPrivateKey aggregatePrivateShares(@NonNull List<TssPrivateShare> privateShares);
+
+    /**
+     * Compute all public shares for all the participants in the scheme.
+     *
+     * @param participantDirectory the participant directory that we should generate the public shares for
+     * @param validTssMessages the {@link TssMessage}s to extract the public shares from. They must be previously
+     * validated.
+     * @return a sorted by the sharedId list of public shares.
+     * @throws IllegalStateException if there aren't enough messages to meet the threshold
+     */
+    @NonNull
+    List<TssPublicShare> computePublicShares(
+            @NonNull TssParticipantDirectory participantDirectory, @NonNull List<TssMessage> validTssMessages);
+
+    /**
+     * Aggregate a threshold number of {@link TssPublicShare}s.
+     * It is the responsibility of the caller to ensure that the list of public shares meets the required
+     * threshold.
+     * If the threshold is not met, the public key returned by this method will be invalid.
+     * This method is used for two distinct purposes:
+     * <ul>
+     *     <li>Aggregating public shares to produce the Ledger ID</li>
+     *     <li>Aggregating public shares derived from all commitments, to produce the public key for a given
+     * share</li>
+     * </ul>
+     *
+     * @param publicShares the public shares to aggregate
+     * @return the interpolated public key
+     */
+    @NonNull
+    PairingPublicKey aggregatePublicShares(@NonNull List<TssPublicShare> publicShares);
+
+    /**
+     * Sign a message using the private share's key.
+     * @param privateShare the private share to sign the message with
+     * @param message the message to sign
+     * @return the signature
+     */
+    @NonNull
+    TssShareSignature sign(@NonNull TssPrivateShare privateShare, @NonNull byte[] message);
+
+    /**
+     * verifies a signature using the participantDirectory and the list of public shares.
+     * @param participantDirectory the pending share claims the TSS message was created for
+     * @param publicShares the public shares to verify the signature with
+     * @param signature the signature to verify
+     * @return if the signature is valid.
+     */
+    boolean verifySignature(
+            @NonNull TssParticipantDirectory participantDirectory,
+            @NonNull List<TssPublicShare> publicShares,
+            @NonNull TssShareSignature signature);
+
+    /**
+     * Aggregate a threshold number of {@link TssShareSignature}s.
+     * It is the responsibility of the caller to ensure that the list of partial signatures meets the required
+     * threshold. If the threshold is not met, the signature returned by this method will be invalid.
+     *
+     * @param partialSignatures the list of signatures to aggregate
+     * @return the interpolated signature
+     */
+    @NonNull
+    PairingSignature aggregateSignatures(@NonNull List<TssShareSignature> partialSignatures);
+}

hedera-node/hedera-app/src/main/java/com/hedera/node/app/tss/api/TssMessage.java

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+/*
+ * Copyright (C) 2024 Hedera Hashgraph, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hedera.node.app.tss.api;
+
+import static java.util.Objects.requireNonNull;
+
+import edu.umd.cs.findbugs.annotations.NonNull;
+
+/**
+ * A message sent as part of either genesis keying, or rekeying.
+ * @param bytes the byte representation of the opaque underlying structure used by the library
+ */
+public record TssMessage(@NonNull byte[] bytes) {
+
+    /**
+     * Constructor
+     * @param bytes bytes the byte representation of the opaque underlying structure used by the library
+     */
+    public TssMessage {
+        requireNonNull(bytes, "bytes must not be null");
+    }
+}