Supported SSH key formats:

• OpenSSH version 1 (with optional password protection, in ISO-8859-1 (for PuTTY) and UTF-8 (for ssh-keygen))
• PuTTY key format version 2 (with optional password protection)
• PuTTY key format version 3 (with optional password protection)
• OpenSSL / PKCS#8 (with optional password protection, in ISO-8859-1 (for PuTTY) and UTF-8 (for ssh-keygen))
• PKCS#1

Supported SSH algorithms:

• RSA
• DSA
• EcDSA (nistp256, nistp384, nistp521)
• EdDSA (Ed25519, Ed448, only with JAVA 15+)

Main classes:

• de.soderer.sshkeyformats.SshKeyReader
• de.soderer.sshkeyformats.SshKeyWriter

This is basically a JAVA 11 project, but it needs JAVA 15 for support of Ed25519 and Ed448 cipher algorithms.

This project depends on BouncyCastle for following reasons:

• EcDSA Keyfactory
• Putty key version 3 "Argon2" password deriving hashing algorithm

Used BouncyCastle libs:

• bcpkix-jdk15on-1.69.jar
• bcprov-jdk15on-1.69.jar

Example code for putty key (ppk) generation and conversion to PKCS#8 (pem)

java.security.KeyPairGenerator keyPairGenerator = java.security.KeyPairGenerator.getInstance("RSA");
keyPairGenerator.initialize(4096);
java.security.KeyPair keyPair = keyPairGenerator.generateKeyPair();
SshKey sshKey = new SshKey(SshKeyFormat.Putty2, "TestKey", keyPair);
SshKeyWriter.writePuttyVersion2Key(new FileOutputStream("test.ppk"), sshKey, "password".toCharArray());
SshKey readSshKey = SshKeyReader.readKey(new FileInputStream("test.ppk"), "password".toCharArray());
SshKeyWriter.writePKCS8Format(new FileOutputStream("test.pem"), readSshKey, "password".toCharArray());

This library is also available via Maven2 repository

<repositories>
	<repository>
		<id>de.soderer</id>
		<url>https://soderer.de/maven2</url>
	</repository>
</repositories>

<dependency>
	<groupId>de.soderer</groupId>
	<artifactId>sshkeyformats</artifactId>
	<version>RELEASE</version>
</dependency>