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Tink is a small cryptographic library that provides a safe, simple, agile and fast way to accomplish some common cryptographic tasks.
// Copyright 2022 Google 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.google.crypto.tink.mac.internal;
import com.google.crypto.tink.config.internal.TinkFipsUtil;
import com.google.crypto.tink.mac.AesCmacKey;
import com.google.crypto.tink.mac.ChunkedMac;
import com.google.crypto.tink.mac.ChunkedMacComputation;
import com.google.crypto.tink.mac.ChunkedMacVerification;
import com.google.crypto.tink.util.Bytes;
import com.google.errorprone.annotations.Immutable;
import java.security.GeneralSecurityException;
/** AES-CMAC implementation of the ChunkedMac interface. */
@Immutable
public final class ChunkedAesCmacImpl implements ChunkedMac {
private static final TinkFipsUtil.AlgorithmFipsCompatibility FIPS =
TinkFipsUtil.AlgorithmFipsCompatibility.ALGORITHM_NOT_FIPS;
@SuppressWarnings("Immutable") // We never change the key.
private final AesCmacKey key;
public ChunkedAesCmacImpl(AesCmacKey key) throws GeneralSecurityException {
if (!FIPS.isCompatible()) {
throw new GeneralSecurityException("Can not use AES-CMAC in FIPS-mode.");
}
this.key = key;
}
@Override
public ChunkedMacComputation createComputation() throws GeneralSecurityException {
return new ChunkedAesCmacComputation(key);
}
@Override
public ChunkedMacVerification createVerification(final byte[] tag)
throws GeneralSecurityException {
if (tag.length < key.getOutputPrefix().size()) {
throw new GeneralSecurityException("Tag too short");
}
if (!key.getOutputPrefix().equals(Bytes.copyFrom(tag, 0, key.getOutputPrefix().size()))) {
throw new GeneralSecurityException("Wrong tag prefix");
}
return new ChunkedAesCmacVerification(key, tag);
}
}
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