Question

我正在尝试使用BouncyCastle的SMIME包来使用ECDSA X509证书创建加密邮件。根据BouncyCastle的发布说明，自1.32（我使用1.46）以来一直支持这一点，但我一直得到一个例外，说明没有找到ECDSA OID的密码。

org.bouncycastle.cms.CMSException：异常包装内容键：无法创建密码：找不到任何支持的提供商 1.2.840.10045.2.1

以下是我正在使用的其中一个测试证书的片段

  Version: V3
  Subject: EMAILADDRESS=bob@example.com
  Signature Algorithm: SHA256withECDSA, OID = 1.2.840.10045.4.3.2

  Key:  EC Public Key

我用来创建加密邮件的代码如下所示：

// allow the use of the BC JCE
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

SMIMEEnvelopedGenerator gen = new SMIMEEnvelopedGenerator();
JceKeyTransRecipientInfoGenerator rig = new JceKeyTransRecipientInfoGenerator(cert);
gen.addRecipientInfoGenerator(rig);

MimeBodyPart msg = new MimeBodyPart();
msg.setText(message);

MimeBodyPart mp = gen.generate(
    msg,
    new JceCMSContentEncryptorBuilder(
        CMSAlgorithm.AES128_CBC).setProvider("BC").build());

Properties props = System.getProperties();
Session session = Session.getDefaultInstance(props, null);

// TODO: This is incorrect.  Perhaps AKA is better?
String to = cert.getSubjectDN().getName();

Address fromUser = new InternetAddress(from);
Address toUser = new InternetAddress(to);

MimeMessage body = new MimeMessage(session);
body.setFrom(fromUser);
body.setRecipient(Message.RecipientType.TO, toUser);
body.setSubject("example encrypted message");
body.setContent(mp.getContent(), mp.getContentType());
body.saveChanges();

body.writeTo(new FileOutputStream(filename));

我确信我做的事情显然是错的，但我现在没有看到它。有什么想法吗？

Answer 1

正如托马斯·波尔丁所建议的那样（上文），需要使用ECDH来完成这项工作。因此，有必要使用JceKeyAgreeRecipientInfoGenerator而不是使用JceKeyTransRecipientInfoGenerator。

SMIMEEnvelopedGenerator gen = new SMIMEEnvelopedGenerator();
JceKeyAgreeRecipientInfoGenerator rig = new JceKeyAgreeRecipientInfoGenerator(CMSAlgorithm.ECDH_SHA1KDF, senderPrivateKey, senderPublicKey, CMSAlgorithm.AES128_WRAP);
rig.setProvider("BC");
gen.addRecipientInfoGenerator(rig);

MimeBodyPart msg = new MimeBodyPart();
msg.setText("This is a secret message");

MimeBodyPart mp = gen.generate(msg, new JceCMSContentEncryptorBuilder(CMSAlgorithm.AES128_CBC).setProvider("BC").build());

Properties props = System.getProperties();
Session session = Session.getDefaultInstance(props, null);

String to = "bob@example.com";

Address fromUser = new InternetAddress("alice@example.com");
Address toUser = new InternetAddress(to);

MimeMessage body = new MimeMessage(session);
body.setFrom(fromUser);
body.setRecipient(Message.RecipientType.TO, toUser);
body.setSubject("example encrypted message");
body.setContent(mp.getContent(), mp.getContentType());
body.saveChanges();

body.writeTo(new FileOutputStream("/tmp/encrypted.msg"));

Answer 2

ECDSA是一种签名算法，而不是加密或密钥交换算法。为了加密消息，您需要收件人的RSA或Diffie-Hellman密钥（可能是ECDH）。

使用EC X509证书加密电子邮件

2 个答案: