Converting PrivateKey to pem string without using bouncycastle

Question

I'm trying to convert a PrivateKey object to pem format string without using bouncycastle. previously I was doing it like this: ``` StringWriter str = new StringWriter(); PEMWriter pemWriter = new PEMWriter(str); pemWriter.writeObject(privKey); pemWriter.close(); str.close(); return str.toString().getBytes(); ``` Now I don't want to use bouncycastle. If I use ``` String code = "-----BEGIN RSA PRIVATE KEY-----
"; String codenew =Base64.encodeBase64String(privKey.getEncoded()); String myOutput = ""; for (String substring : Splitter.fixedLength(64).split(codenew)) { myOutput += substring + "
"; } code += myOutput.substring(0, myOutput.length() - 1); code += "
-----END RSA PRIVATE KEY-----"; return code.getBytes(); ``` The code above works and I'm able to decrypt using openssl by passing this byte[]. Now, my problem is, if I'm printing the pem string value for the above two piece of code, they are different. If I'm using the below openssl command $ openssl pkcs12 -in receiver.p12 -out…

Accepted Answer

PEMWriter class from BouncyCastle stores private key in PKCS#1 format (for more details please see RsaPrivateKey stucture defined in RFC 3447):

Your code stores private key in PKCS#8 format (for more details please see PrivateKeyInfo structure defined in RFC 5208):

PKCS#1 defines how to store RSA keys while PKCS#8 defines an envelope that can store any asymmetric key pair. As you can see on the attached pictures PKCS#8 just envelopes PKCS#1 and specifies that key is usable with RSA algorithm.

Converting PrivateKey to pem string without using bouncycastle

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