Update from #1926

Author: gefeili

pg/src/main/java/org/bouncycastle/openpgp/operator/PBEDataDecryptorFactory.java

@@ -7,6 +7,8 @@
 
 /**
  * A factory for performing PBE decryption operations.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation to use for symmetric decryption of SKESK (symmetric-key-encrypted session-key) packets.
  */
 public abstract class PBEDataDecryptorFactory
     implements PGPDataDecryptorFactory

pg/src/main/java/org/bouncycastle/openpgp/operator/PGPContentSignerBuilder.java

@@ -3,6 +3,11 @@
 import org.bouncycastle.openpgp.PGPException;
 import org.bouncycastle.openpgp.PGPPrivateKey;
 
+/**
+ * Builder for {@link PGPContentSigner} objects.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation to use for the {@link PGPContentSigner}.
+ */
 public interface PGPContentSignerBuilder
 {
     PGPContentSigner build(final int signatureType, final PGPPrivateKey privateKey)

pg/src/main/java/org/bouncycastle/openpgp/operator/PGPContentVerifierBuilderProvider.java

@@ -2,6 +2,12 @@
 
 import org.bouncycastle.openpgp.PGPException;
 
+/**
+ * Provider for {@link PGPContentVerifierBuilder} instances.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation of {@link PGPContentVerifierBuilder} (builder for objects check signatures for correctness)
+ * to provide.
+ */
 public interface PGPContentVerifierBuilderProvider
 {
     PGPContentVerifierBuilder get(int keyAlgorithm, int hashAlgorithm)

pg/src/main/java/org/bouncycastle/openpgp/operator/PGPDigestCalculatorProvider.java

@@ -5,6 +5,8 @@
 
 /**
  * A factory for digest algorithms.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation to use for calculating PGP digests.
  */
 public interface PGPDigestCalculatorProvider
 {

pg/src/main/java/org/bouncycastle/openpgp/operator/PublicKeyDataDecryptorFactory.java

@@ -4,6 +4,11 @@
 import org.bouncycastle.bcpg.PublicKeyEncSessionPacket;
 import org.bouncycastle.openpgp.PGPException;
 
+/**
+ * Factory for public-key based {@link PGPDataDecryptor PGPDataDecryptors}.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation to use to decrypt OpenPGP messages that were encrypted to a public-key.
+ */
 public interface PublicKeyDataDecryptorFactory
     extends PGPDataDecryptorFactory
 {

pg/src/main/java/org/bouncycastle/openpgp/operator/PublicKeyKeyEncryptionMethodGenerator.java

@@ -11,6 +11,11 @@
 import java.io.IOException;
 import java.math.BigInteger;
 
+/**
+ * Abstract generator class for encryption methods that produce PKESK (public-key encrypted session key) packets.
+ * PKESKs are used when encrypting a message for a recipients public key.
+ * The purpose of this class is to allow subclasses to decide, which implementation to use.
+ */
 public abstract class PublicKeyKeyEncryptionMethodGenerator
     extends PGPKeyEncryptionMethodGenerator
 {

pg/src/main/java/org/bouncycastle/openpgp/operator/SessionKeyDataDecryptorFactory.java

@@ -2,6 +2,12 @@
 
 import org.bouncycastle.openpgp.PGPSessionKey;
 
+/**
+ * Factory for {@link PGPDataDecryptor} objects that use a {@link PGPSessionKey} to decrypt the content of an
+ * OpenPGP message.
+ * The purpose of this class is to act as an abstract factory, whose subclasses can decide, which concrete
+ * implementation to use for message decryption.
+ */
 public interface SessionKeyDataDecryptorFactory
     extends PGPDataDecryptorFactory
 {