src/main/java/com/android/apksig/internal/apk/ContentDigestAlgorithm.java

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * 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.android.apksig.internal.apk;

/** APK Signature Scheme v2 content digest algorithm. */
public enum ContentDigestAlgorithm {
    /** SHA2-256 over 1 MB chunks. */
    CHUNKED_SHA256(1, "SHA-256", 256 / 8),

    /** SHA2-512 over 1 MB chunks. */
    CHUNKED_SHA512(2, "SHA-512", 512 / 8),

    /** SHA2-256 over 4 KB chunks for APK verity. */
    VERITY_CHUNKED_SHA256(3, "SHA-256", 256 / 8),

    /** Non-chunk SHA2-256. */
    SHA256(4, "SHA-256", 256 / 8);

    private final int mId;
    private final String mJcaMessageDigestAlgorithm;
    private final int mChunkDigestOutputSizeBytes;

    private ContentDigestAlgorithm(
            int id, String jcaMessageDigestAlgorithm, int chunkDigestOutputSizeBytes) {
        mId = id;
        mJcaMessageDigestAlgorithm = jcaMessageDigestAlgorithm;
        mChunkDigestOutputSizeBytes = chunkDigestOutputSizeBytes;
    }

    /** Returns the ID of the digest algorithm used on the APK. */
    public int getId() {
        return mId;
    }

    /**
     * Returns the {@link java.security.MessageDigest} algorithm used for computing digests of
     * chunks by this content digest algorithm.
     */
    String getJcaMessageDigestAlgorithm() {
        return mJcaMessageDigestAlgorithm;
    }

    /** Returns the size (in bytes) of the digest of a chunk of content. */
    int getChunkDigestOutputSizeBytes() {
        return mChunkDigestOutputSizeBytes;
    }
}