java - 将 SubjectPublicKeyInfo 格式的公钥转换为 RSAPublicKey 格式 java

Question

PublicKey.getEncoded()，返回一个字节数组，其中包含 SubjectPublicKeyInfo (x.509) 格式的公钥，如何将其转换为 RSA 公钥编码？

Answer 1

使用 Bouncy Castle 的SubjectPublicKeyInfo，像这样：

byte[] encoded = publicKey.getEncoded();
SubjectPublicKeyInfo subjectPublicKeyInfo = SubjectPublicKeyInfo.getInstance(
        ASN1Sequence.getInstance(encoded));
byte[] otherEncoded = subjectPublicKeyInfo.parsePublicKey().getEncoded();

Answer 2

没有 BouncyCastle：

PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(publicKeyBinary));                

Answer 3

以下代码片段对我有用，但必须使用 BouncyCastle。

byte[] keyBytes = key.getEncoded(); // X.509 for public key
SubjectPublicKeyInfo subPkInfo = new SubjectPublicKeyInfo((ASN1Sequence)ASN1Object.fromByteArray(keyBytes));
byte[] rsaformat = subPkInfo.getPublicKey().getDEREncoded();