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

Question

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

Answer 1

使用Bouncy Castle的SubjectPublicKeyInfo，如下所示：

byte[] encoded = publicKey.getEncoded();
SubjectPublicKeyInfo subjectPublicKeyInfo = new SubjectPublicKeyInfo(
    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，但不得不使用BouncyCastle。

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