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performance: add license headers and some documentation

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This commit is contained in:
Vincent Breitmoser
2016-02-10 17:08:00 +01:00
parent 3bf6a00250
commit 01b165ea88
5 changed files with 72 additions and 14 deletions
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22
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/util/Passphrase.java
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@@ -1,5 +1,6 @@
/*
* Copyright (C) 2015 Dominik Schürmann <dominik@dominikschuermann.de>
* Copyright (C) 2016 Vincent Breitmoser <look@my.amazin.horse>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -32,8 +33,13 @@ import java.util.Map.Entry;
/**
* Passwords should not be stored as Strings in memory.
* This class wraps a char[] that can be erased after it is no longer used.
* This class wraps a char[] array that is overwritten before the object is freed, to avoid
* keeping passphrases in memory as much as possible.
*
* In addition to the raw passphrases, this class can cache the session key output of an applied
* S2K algorithm for a given set of S2K parameters. Since S2K operations are very expensive, this
* mechanism should be used to cache session keys whenever possible.
*
* See also:
* <p/>
* http://docs.oracle.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html#PBEEx
@@ -43,7 +49,7 @@ import java.util.Map.Entry;
*/
public class Passphrase implements Parcelable {
private char[] mPassphrase;
HashMap<ComparableS2K, byte[]> mCachedSessionKeys;
private HashMap<ComparableS2K, byte[]> mCachedSessionKeys;
/**
* According to http://stackoverflow.com/a/15844273 EditText is not using String internally
@@ -93,14 +99,20 @@ public class Passphrase implements Parcelable {
return mPassphrase.length;
}
public byte[] getCachedSessionKeyForAlgorithm(int keyEncryptionAlgorithm, S2K s2k) {
/** @return A cached session key, or null if none exists for the given parameters. */
public byte[] getCachedSessionKeyForParameters(int keyEncryptionAlgorithm, S2K s2k) {
if (mCachedSessionKeys == null) {
return null;
}
return mCachedSessionKeys.get(new ComparableS2K(keyEncryptionAlgorithm, s2k));
}
public void addCachedSessionKey(int keyEncryptionAlgorithm, S2K s2k, byte[] sessionKey) {
/** Adds a session key for a set of s2k parameters to this Passphrase object's
* cache. The caller should make sure that the supplied session key is the result
* of an S2K operation applied to exactly the passphrase stored by this object
* with the given parameters.
*/
public void addCachedSessionKeyForParameters(int keyEncryptionAlgorithm, S2K s2k, byte[] sessionKey) {
if (mCachedSessionKeys == null) {
mCachedSessionKeys = new HashMap<>();
}