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Add OAEP encoding that uses SHA-256 #98

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Add OAEP encoding that uses SHA-256 #98

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63959e1
add RSA-OAEP implementation using SHA256
matehat Jan 10, 2021
aa041cd
Apply null safety migration
matehat Mar 12, 2021
b7d028c
fix algorithm name to not clash wutg with OAEP
matehat Apr 18, 2021
dc50bf9
export OAEP SHA256 encoding
matehat Apr 18, 2021
63d30ff
use a single OAEPEncoding class
matehat Apr 19, 2021
4d443b8
Add ability to provide custom digest
matehat Apr 19, 2021
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28 changes: 23 additions & 5 deletions lib/asymmetric/oaep.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ import 'package:pointycastle/src/registry/registry.dart';
import 'package:pointycastle/src/impl/base_asymmetric_block_cipher.dart';
import 'package:pointycastle/random/fortuna_random.dart';
import 'package:pointycastle/digests/sha1.dart';
import 'package:pointycastle/digests/sha256.dart';

typedef DigestFactory = Digest Function();

/// RSAES-OAEP v2.0
///
Expand All @@ -27,7 +30,7 @@ import 'package:pointycastle/digests/sha1.dart';
///
/// Currently, this implementation has the following restrictions:
///
/// - the hash function is hard-coded to be SHA-1;
/// - the hash function is hard-coded to be SHA-1 or SHA-256;
/// - the mask generation function is hard-coded to MGF1; and
/// - it cannot accept any _encoding parameters_ (that is, _P_ is always empty)

Expand All @@ -42,7 +45,7 @@ class OAEPEncoding extends BaseAsymmetricBlockCipher {
});

/// Hash function used by the EME-OAEP (Encoding Method for Encryption OAEP).
Digest hash = SHA1Digest();
Digest hash;

/// Hash function used by the MGF1 Mask Generation Function.
late Digest mgf1Hash;
Expand All @@ -51,16 +54,31 @@ class OAEPEncoding extends BaseAsymmetricBlockCipher {
///
/// Note: in this implementation the encoding parameters is always zero
/// octets. There is no mechanism to provide encoding parameters.
Uint8List defHash = Uint8List(SHA1Digest().digestSize);
Uint8List defHash;

final AsymmetricBlockCipher _engine;
late SecureRandom _random;
late bool _forEncryption;

OAEPEncoding(this._engine) {
SHA1Digest().doFinal(defHash, 0);
OAEPEncoding._(DigestFactory digestFactory, this._engine)
: hash = digestFactory(),
defHash = Uint8List(digestFactory().digestSize) {
digestFactory().doFinal(defHash, 0);
}

factory OAEPEncoding(AsymmetricBlockCipher engine) =>
OAEPEncoding.withSHA1(engine);

factory OAEPEncoding.withSHA1(AsymmetricBlockCipher engine) =>
OAEPEncoding._(() => SHA1Digest(), engine);

factory OAEPEncoding.withSHA256(AsymmetricBlockCipher engine) =>
OAEPEncoding._(() => SHA256Digest(), engine);

factory OAEPEncoding.withCustomDigest(
DigestFactory digestFactory, AsymmetricBlockCipher engine) =>
OAEPEncoding._(digestFactory, engine);

@override
String get algorithmName => '${_engine.algorithmName}/OAEP';

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