First working prototype

pgpainless-core/src/main/java/org/pgpainless/certificate_store/CertificateParser.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.certificate_store;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import org.bouncycastle.openpgp.PGPPublicKeyRing;
+import org.bouncycastle.util.encoders.Base64;
+import org.pgpainless.PGPainless;
+import org.pgpainless.key.OpenPgpFingerprint;
+import pgp.certificate_store.Certificate;
+import pgp.certificate_store.ParserBackend;
+
+public class CertificateParser implements ParserBackend {
+
+    @Override
+    public Certificate readCertificate(InputStream inputStream) throws IOException {
+        final PGPPublicKeyRing certificate = PGPainless.readKeyRing().publicKeyRing(inputStream);
+        return new Certificate() {
+            @Override
+            public String getFingerprint() {
+                return OpenPgpFingerprint.of(certificate).toString().toLowerCase();
+            }
+
+            @Override
+            public InputStream getInputStream() throws IOException {
+                return new ByteArrayInputStream(certificate.getEncoded());
+            }
+
+            @Override
+            public String getTag() throws IOException {
+                MessageDigest digest;
+                try {
+                    digest = MessageDigest.getInstance("SHA-256");
+                } catch (NoSuchAlgorithmException e) {
+                    throw new AssertionError("No MessageDigest for SHA-256 instantiated, although BC is on the classpath: " + e.getMessage());
+                }
+                digest.update(certificate.getEncoded());
+                return Base64.toBase64String(digest.digest());
+            }
+        };
+    }
+}

pgpainless-core/src/main/java/org/pgpainless/certificate_store/package-info.java

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+// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+/**
+ * Implementations of the module pgp-certificate-store using pgpainless-core.
+ */
+package org.pgpainless.certificate_store;