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Code Issues Releases Wiki Activity

Use higher s2k count

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This commit is contained in:
Dominik Schürmann 2014-08-19 11:11:58 +02:00
parent d131693bb8
commit 4a280f6ba3
1 changed files with 29 additions and 10 deletions
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39
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpKeyOperation.java
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@ -25,7 +25,6 @@ import org.spongycastle.bcpg.SymmetricKeyAlgorithmTags;
import org.spongycastle.bcpg.sig.Features;
import org.spongycastle.bcpg.sig.KeyFlags;
import org.spongycastle.jce.spec.ElGamalParameterSpec;
import org.spongycastle.openpgp.PGPEncryptedData;
import org.spongycastle.openpgp.PGPException;
import org.spongycastle.openpgp.PGPKeyPair;
import org.spongycastle.openpgp.PGPPrivateKey;
@ -104,6 +103,26 @@ public class PgpKeyOperation {
CompressionAlgorithmTags.ZIP
};
/*
* Note: s2kcount is a number between 0 and 0xff that controls the
* number of times to iterate the password hash before use. More
* iterations are useful against offline attacks, as it takes more
* time to check each password. The actual number of iterations is
* rather complex, and also depends on the hash function in use.
* Refer to Section 3.7.1.3 in rfc4880.txt. Bigger numbers give
* you more iterations. As a rough rule of thumb, when using
* SHA256 as the hashing function, 0x10 gives you about 64
* iterations, 0x20 about 128, 0x30 about 256 and so on till 0xf0,
* or about 1 million iterations. The maximum you can go to is
* 0xff, or about 2 million iterations. I'll use 0xc0 as a
* default -- about 130,000 iterations.
*
* http://kbsriram.com/2013/01/generating-rsa-keys-with-bouncycastle.html
*/
private static final int SECRET_KEY_ENCRYPTOR_HASH_ALGO = HashAlgorithmTags.SHA512;
private static final int SECRET_KEY_ENCRYPTOR_SYMMETRIC_ALGO = SymmetricKeyAlgorithmTags.AES_256;
private static final int SECRET_KEY_ENCRYPTOR_S2K_COUNT = 0xc0;
public PgpKeyOperation(Progressable progress) {
super();
if (progress != null) {
@ -250,10 +269,10 @@ public class PgpKeyOperation {
progress(R.string.progress_building_master_key, 40);
// Build key encrypter and decrypter based on passphrase
PGPDigestCalculator sha512Calc = new JcaPGPDigestCalculatorProviderBuilder()
.build().get(HashAlgorithmTags.SHA512);
PGPDigestCalculator encryptorHashCalc = new JcaPGPDigestCalculatorProviderBuilder()
.build().get(SECRET_KEY_ENCRYPTOR_HASH_ALGO);
PBESecretKeyEncryptor keyEncryptor = new JcePBESecretKeyEncryptorBuilder(
PGPEncryptedData.AES_256, sha512Calc)
SECRET_KEY_ENCRYPTOR_SYMMETRIC_ALGO, encryptorHashCalc, SECRET_KEY_ENCRYPTOR_S2K_COUNT)
.setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build("".toCharArray());
// NOTE: only SHA1 is supported for key checksum calculations.
@ -705,10 +724,10 @@ public class PgpKeyOperation {
PGPSecretKey sKey; {
// Build key encrypter and decrypter based on passphrase
PGPDigestCalculator sha512Calc = new JcaPGPDigestCalculatorProviderBuilder()
.build().get(HashAlgorithmTags.SHA512);
PGPDigestCalculator encryptorHashCalc = new JcaPGPDigestCalculatorProviderBuilder()
.build().get(SECRET_KEY_ENCRYPTOR_HASH_ALGO);
PBESecretKeyEncryptor keyEncryptor = new JcePBESecretKeyEncryptorBuilder(
PGPEncryptedData.AES_256, sha512Calc)
SECRET_KEY_ENCRYPTOR_SYMMETRIC_ALGO, encryptorHashCalc, SECRET_KEY_ENCRYPTOR_S2K_COUNT)
.setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(passphrase.toCharArray());
// NOTE: only SHA1 is supported for key checksum calculations.
@ -731,13 +750,13 @@ public class PgpKeyOperation {
log.add(LogLevel.INFO, LogType.MSG_MF_PASSPHRASE, indent);
indent += 1;
PGPDigestCalculator sha512Calc = new JcaPGPDigestCalculatorProviderBuilder().build()
.get(HashAlgorithmTags.SHA512);
PGPDigestCalculator encryptorHashCalc = new JcaPGPDigestCalculatorProviderBuilder().build()
.get(SECRET_KEY_ENCRYPTOR_HASH_ALGO);
PBESecretKeyDecryptor keyDecryptor = new JcePBESecretKeyDecryptorBuilder().setProvider(
Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(passphrase.toCharArray());
// Build key encryptor based on new passphrase
PBESecretKeyEncryptor keyEncryptorNew = new JcePBESecretKeyEncryptorBuilder(
PGPEncryptedData.AES_256, sha512Calc)
SECRET_KEY_ENCRYPTOR_SYMMETRIC_ALGO, encryptorHashCalc, SECRET_KEY_ENCRYPTOR_S2K_COUNT)
.setProvider(Constants.BOUNCY_CASTLE_PROVIDER_NAME).build(
saveParcel.mNewPassphrase.toCharArray());