CODEWITHSUNDEEP
javacryptographyrsapkcs#1
Ashish Kumar Shah
Ashish Kumar Shah

Reputation: 532

Converting A public key in SubjectPublicKeyInfo format to RSAPublicKey format java

The PublicKey.getEncoded(), returns a byte array containing the public key in SubjectPublicKeyInfo (x.509) format, how do i convert it to RSA public key encoding?

Upvotes: 13

Views: 29964

Answers (3)

martijno
martijno

Reputation: 1783

Use Bouncy Castle's SubjectPublicKeyInfo, like this:

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

Upvotes: 21

Michael Webster
Michael Webster

Reputation: 59

Without BouncyCastle:

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

Upvotes: 5

Ashish Kumar Shah
Ashish Kumar Shah

Reputation: 532

The following snippet of code worked for me, had to use BouncyCastle though.

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

Upvotes: 0

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