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BAEL-4219 - How to read .pem file to get private and public key (eugenp#9676)
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‎core-java-modules/core-java-security-2/src/main/java/com/baeldung/pem/JavaSecurityPemUtils.java‎

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package com.baeldung.pem;
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import org.apache.commons.codec.binary.Base64;
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import java.io.File;
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import java.io.IOException;
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import java.nio.charset.Charset;
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import java.nio.file.Files;
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import java.security.GeneralSecurityException;
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import java.security.KeyFactory;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import java.security.spec.PKCS8EncodedKeySpec;
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import java.security.spec.X509EncodedKeySpec;
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public class JavaSecurityPemUtils {
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public static RSAPrivateKey readPKCS8PrivateKey(File file) throws GeneralSecurityException, IOException {
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String key = new String(Files.readAllBytes(file.toPath()), Charset.defaultCharset());
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String privateKeyPEM = key
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.replace("-----BEGIN PRIVATE KEY-----", "")
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.replaceAll(System.lineSeparator(), "")
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.replace("-----END PRIVATE KEY-----", "");
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byte[] encoded = Base64.decodeBase64(privateKeyPEM);
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KeyFactory keyFactory = KeyFactory.getInstance("RSA");
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PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(encoded);
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return (RSAPrivateKey) keyFactory.generatePrivate(keySpec);
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}
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public static RSAPublicKey readX509PublicKey(File file) throws GeneralSecurityException, IOException {
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String key = new String(Files.readAllBytes(file.toPath()), Charset.defaultCharset());
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String publicKeyPEM = key
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.replace("-----BEGIN PUBLIC KEY-----", "")
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.replaceAll(System.lineSeparator(), "")
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.replace("-----END PUBLIC KEY-----", "");
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byte[] encoded = Base64.decodeBase64(publicKeyPEM);
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KeyFactory keyFactory = KeyFactory.getInstance("RSA");
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X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encoded);
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return (RSAPublicKey) keyFactory.generatePublic(keySpec);
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}
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}

‎core-java-modules/core-java-security-2/src/main/resources/pem/private-key-pkcs8.pem‎

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-----BEGIN PRIVATE KEY-----
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MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCyO0YiTxLEP44S
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IGk/b9MlQAXS6nC4oYyTrAfxHCi/zxW/MmtWbY0K2JxOTkVSD5QbmvwkCutXi0k9
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EdDK+orAXg2KSy686O/cfIh/iho6FmNPyEOd7UF+/5wWpknrUaTQyMA2H9Pmr2/E
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RH/tN1Q0cqmhFX41WUo3lsRT81DkVCNVeJx+zDGHpjp+XY8gWpPYJ+MP4WQE9TWJ
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P2rIlgcDfwhG/A21yK0WAJ5nB0Y+jGI8+HVYdjxXGlRUG//YmxS2sH+sAhsapmjE
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Aha+KMk972jVNjdWU7OT0BJnUB5q286Kv6INUnk6kqYufNzjpCAY9SyMjKjpKN71
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3Gka2gZBAgMBAAECggEAFlPam12wiik0EQ1CYhIOL3JvyFZaPKbwR2ebrxbJ/A1j
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OgqE69TZgGxWWHDxui/9a9/kildb2CG40Q+0SllMnICrzZFRj5TWx5ZKOz//vRsk
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4c/CuLwKInC/Cw9V30bhEM61VZJzJ0j/BWVXaU4vHEro+ScKIoDHDWOzwJiQn6m9
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C+Ti5lFpax3hx8ZrgPqmBCFYNvErrWkOr7mCYl0jS+E22c68yn8+LjdlF1LWUa6N
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zutk3MPj5UwEyR0h7EZReCeGkPTMQNyOBhDcmAtlEno4fjtZzUDHRjh8/QpG1Mz/
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alavvrkjswc1DmRUOdgiYu+Waxan5noBhxEAvd/hyQKBgQDjYJD0n+m0tUrpNtX0
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+mdzHstClHrpx5oNxs4sIBjCoCwEXaSpeY8+JxCdnZ6n29mLZLq/wPXxZ3EJcOSZ
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PYUvZJfV/IUvoLPFbtT3ILzDTcAAeHj2GAOpzYP8J1JSFsc78ZjKMF1XeNjXcq8T
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XNXoWfY7N/fShoycVeG42JJCFwKBgQDIqvHL0QfJ8r6yM8Efj7Zq6Wa4C9okORes
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8UVWfBoO6UOWvpK+D9IjnaEisJcnEalwNi8/eKudR9hfvmzATV+t3YJIgktto3TT
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BWLsEyniNU4vSTl7GPBrV2xabWogbChlt7TXUfw6YogaBKm43snYXBbJFc+NcpQH
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ONB5igppZwKBgGDyYHvc3wGsttb/CXTde1RLUfD+a/XXpCixlmCcAtKhBoOKBdY4
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vUmL0HrTpLz/cR8NAM8XkAWwzDJxTxbDc1EEu/SCKatoAp5wph8Ed1dyhCXvN+v9
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yzoQJXFStrfHfIVjenji7DmKjjI2dM11rMLX8LPJJkI+Gh/iQk7VEG9bAoGAH/aS
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sztleTZwR6RUw7k5fkgVM4W3xoNNkR+RQthbsjpXqMBMUXflqgSmsQbd3LxEd/o5
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hmurMk9KWN3VJsBsWB5rbS9L4nfh2OcHvcDDsCN7g66vODtduEthl/nLqMRxnton
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NRD7EzW0pihN/IOINS1d98PAnrA8gfX7xxBE3ksCgYBvoljHGjvy3bPJ++vDGKJK
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y6JuEeRVzgdPXEb60uU+BR7kdh+MMsZLmgfFTgza3R+/xeZcC/cuOPsbzeooRQi/
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9NpKwSCXjVNk9nglUWBoPRh4uYqrArWn+HoR7MI/BxeRJm5e1+ii8P19Y9joX5s0
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Q3OLn8GeH56ClJmNiWDhsA==
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-----END PRIVATE KEY-----

‎core-java-modules/core-java-security-2/src/main/resources/pem/public-key.pem‎

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-----BEGIN PUBLIC KEY-----
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MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsjtGIk8SxD+OEiBpP2/T
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JUAF0upwuKGMk6wH8Rwov88VvzJrVm2NCticTk5FUg+UG5r8JArrV4tJPRHQyvqK
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wF4NiksuvOjv3HyIf4oaOhZjT8hDne1Bfv+cFqZJ61Gk0MjANh/T5q9vxER/7TdU
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NHKpoRV+NVlKN5bEU/NQ5FQjVXicfswxh6Y6fl2PIFqT2CfjD+FkBPU1iT9qyJYH
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A38IRvwNtcitFgCeZwdGPoxiPPh1WHY8VxpUVBv/2JsUtrB/rAIbGqZoxAIWvijJ
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Pe9o1TY3VlOzk9ASZ1AeatvOir+iDVJ5OpKmLnzc46QgGPUsjIyo6Sje9dxpGtoG
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QQIDAQAB
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-----END PUBLIC KEY-----

‎core-java-modules/core-java-security-2/src/test/java/com/baeldung/pem/JavaSecurityPemUtilsUnitTest.java‎

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package com.baeldung.pem;
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import org.junit.jupiter.api.Test;
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import java.io.File;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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public class JavaSecurityPemUtilsUnitTest {
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@Test
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public void whenReadPublicKeyFromPEMFile_thenSuccess() throws Exception {
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File pemFile = new File(JavaSecurityPemUtilsUnitTest.class.getResource("/pem/public-key.pem").getFile());
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RSAPublicKey publicKey = JavaSecurityPemUtils.readX509PublicKey(pemFile);
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assertEquals("X.509", publicKey.getFormat());
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assertEquals("RSA", publicKey.getAlgorithm());
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}
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@Test
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public void whenReadPrivateKeyFromPEMFile_thenSuccess() throws Exception {
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File pemFile = new File(JavaSecurityPemUtilsUnitTest.class.getResource("/pem/private-key-pkcs8.pem").getFile());
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RSAPrivateKey privateKey = JavaSecurityPemUtils.readPKCS8PrivateKey(pemFile);
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assertEquals("PKCS#8", privateKey.getFormat());
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assertEquals("RSA", privateKey.getAlgorithm());
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}
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}

‎libraries-security/src/main/java/com/baeldung/pem/BouncyCastlePemUtils.java‎

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package com.baeldung.pem;
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import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
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import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
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import org.bouncycastle.openssl.PEMParser;
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import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
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import org.bouncycastle.util.io.pem.PemObject;
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import org.bouncycastle.util.io.pem.PemReader;
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import java.io.File;
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import java.io.FileReader;
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import java.io.IOException;
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import java.security.KeyFactory;
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import java.security.NoSuchAlgorithmException;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import java.security.spec.InvalidKeySpecException;
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import java.security.spec.PKCS8EncodedKeySpec;
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import java.security.spec.X509EncodedKeySpec;
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public class BouncyCastlePemUtils {
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public static RSAPublicKey readX509PublicKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
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KeyFactory factory = KeyFactory.getInstance("RSA");
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try (FileReader keyReader = new FileReader(file);
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PemReader pemReader = new PemReader(keyReader)) {
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PemObject pemObject = pemReader.readPemObject();
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byte[] content = pemObject.getContent();
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X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(content);
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return (RSAPublicKey) factory.generatePublic(pubKeySpec);
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}
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}
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public static RSAPublicKey readX509PublicKeySecondApproach(File file) throws IOException {
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try (FileReader keyReader = new FileReader(file)) {
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PEMParser pemParser = new PEMParser(keyReader);
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JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
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SubjectPublicKeyInfo publicKeyInfo = SubjectPublicKeyInfo.getInstance(pemParser.readObject());
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return (RSAPublicKey) converter.getPublicKey(publicKeyInfo);
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}
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}
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public static RSAPrivateKey readPKCS8PrivateKey(File file) throws InvalidKeySpecException, IOException, NoSuchAlgorithmException {
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KeyFactory factory = KeyFactory.getInstance("RSA");
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try (FileReader keyReader = new FileReader(file);
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PemReader pemReader = new PemReader(keyReader)) {
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PemObject pemObject = pemReader.readPemObject();
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byte[] content = pemObject.getContent();
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PKCS8EncodedKeySpec privKeySpec = new PKCS8EncodedKeySpec(content);
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return (RSAPrivateKey) factory.generatePrivate(privKeySpec);
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}
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}
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public static RSAPrivateKey readPKCS8PrivateKeySecondApproach(File file) throws IOException {
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try (FileReader keyReader = new FileReader(file)) {
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PEMParser pemParser = new PEMParser(keyReader);
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JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
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PrivateKeyInfo privateKeyInfo = PrivateKeyInfo.getInstance(pemParser.readObject());
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return (RSAPrivateKey) converter.getPrivateKey(privateKeyInfo);
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}
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}
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}

‎libraries-security/src/main/resources/pem/private-key-pkcs8.pem‎

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-----BEGIN PRIVATE KEY-----
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MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCyO0YiTxLEP44S
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IGk/b9MlQAXS6nC4oYyTrAfxHCi/zxW/MmtWbY0K2JxOTkVSD5QbmvwkCutXi0k9
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EdDK+orAXg2KSy686O/cfIh/iho6FmNPyEOd7UF+/5wWpknrUaTQyMA2H9Pmr2/E
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RH/tN1Q0cqmhFX41WUo3lsRT81DkVCNVeJx+zDGHpjp+XY8gWpPYJ+MP4WQE9TWJ
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P2rIlgcDfwhG/A21yK0WAJ5nB0Y+jGI8+HVYdjxXGlRUG//YmxS2sH+sAhsapmjE
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Aha+KMk972jVNjdWU7OT0BJnUB5q286Kv6INUnk6kqYufNzjpCAY9SyMjKjpKN71
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3Gka2gZBAgMBAAECggEAFlPam12wiik0EQ1CYhIOL3JvyFZaPKbwR2ebrxbJ/A1j
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OgqE69TZgGxWWHDxui/9a9/kildb2CG40Q+0SllMnICrzZFRj5TWx5ZKOz//vRsk
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4c/CuLwKInC/Cw9V30bhEM61VZJzJ0j/BWVXaU4vHEro+ScKIoDHDWOzwJiQn6m9
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C+Ti5lFpax3hx8ZrgPqmBCFYNvErrWkOr7mCYl0jS+E22c68yn8+LjdlF1LWUa6N
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zutk3MPj5UwEyR0h7EZReCeGkPTMQNyOBhDcmAtlEno4fjtZzUDHRjh8/QpG1Mz/
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alavvrkjswc1DmRUOdgiYu+Waxan5noBhxEAvd/hyQKBgQDjYJD0n+m0tUrpNtX0
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PYUvZJfV/IUvoLPFbtT3ILzDTcAAeHj2GAOpzYP8J1JSFsc78ZjKMF1XeNjXcq8T
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XNXoWfY7N/fShoycVeG42JJCFwKBgQDIqvHL0QfJ8r6yM8Efj7Zq6Wa4C9okORes
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8UVWfBoO6UOWvpK+D9IjnaEisJcnEalwNi8/eKudR9hfvmzATV+t3YJIgktto3TT
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vUmL0HrTpLz/cR8NAM8XkAWwzDJxTxbDc1EEu/SCKatoAp5wph8Ed1dyhCXvN+v9
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yzoQJXFStrfHfIVjenji7DmKjjI2dM11rMLX8LPJJkI+Gh/iQk7VEG9bAoGAH/aS
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sztleTZwR6RUw7k5fkgVM4W3xoNNkR+RQthbsjpXqMBMUXflqgSmsQbd3LxEd/o5
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hmurMk9KWN3VJsBsWB5rbS9L4nfh2OcHvcDDsCN7g66vODtduEthl/nLqMRxnton
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NRD7EzW0pihN/IOINS1d98PAnrA8gfX7xxBE3ksCgYBvoljHGjvy3bPJ++vDGKJK
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y6JuEeRVzgdPXEb60uU+BR7kdh+MMsZLmgfFTgza3R+/xeZcC/cuOPsbzeooRQi/
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9NpKwSCXjVNk9nglUWBoPRh4uYqrArWn+HoR7MI/BxeRJm5e1+ii8P19Y9joX5s0
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Q3OLn8GeH56ClJmNiWDhsA==
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-----END PRIVATE KEY-----

‎libraries-security/src/main/resources/pem/public-key.pem‎

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-----BEGIN PUBLIC KEY-----
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MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAsjtGIk8SxD+OEiBpP2/T
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JUAF0upwuKGMk6wH8Rwov88VvzJrVm2NCticTk5FUg+UG5r8JArrV4tJPRHQyvqK
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wF4NiksuvOjv3HyIf4oaOhZjT8hDne1Bfv+cFqZJ61Gk0MjANh/T5q9vxER/7TdU
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NHKpoRV+NVlKN5bEU/NQ5FQjVXicfswxh6Y6fl2PIFqT2CfjD+FkBPU1iT9qyJYH
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A38IRvwNtcitFgCeZwdGPoxiPPh1WHY8VxpUVBv/2JsUtrB/rAIbGqZoxAIWvijJ
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Pe9o1TY3VlOzk9ASZ1AeatvOir+iDVJ5OpKmLnzc46QgGPUsjIyo6Sje9dxpGtoG
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QQIDAQAB
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-----END PUBLIC KEY-----

‎libraries-security/src/test/java/com/baeldung/pem/BouncyCastlePemUtilsUnitTest.java‎

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package com.baeldung.pem;
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import org.junit.jupiter.api.Test;
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import java.io.File;
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import java.security.interfaces.RSAPrivateKey;
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import java.security.interfaces.RSAPublicKey;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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public class BouncyCastlePemUtilsUnitTest {
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@Test
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public void whenReadPublicKeyFromPEMFile_thenSuccess() throws Exception {
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File pemFile = new File(BouncyCastlePemUtilsUnitTest.class.getResource("/pem/public-key.pem").getFile());
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RSAPublicKey publicKey1 = BouncyCastlePemUtils.readX509PublicKey(pemFile);
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RSAPublicKey publicKey2 = BouncyCastlePemUtils.readX509PublicKeySecondApproach(pemFile);
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assertEquals("X.509", publicKey1.getFormat());
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assertEquals("RSA", publicKey1.getAlgorithm());
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assertEquals("X.509", publicKey2.getFormat());
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assertEquals("RSA", publicKey2.getAlgorithm());
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}
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@Test
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public void whenReadPrivateKeyFromPEMFile_thenSuccess() throws Exception {
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File pemFile = new File(BouncyCastlePemUtilsUnitTest.class.getResource("/pem/private-key-pkcs8.pem").getFile());
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RSAPrivateKey privateKey1 = BouncyCastlePemUtils.readPKCS8PrivateKey(pemFile);
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RSAPrivateKey privateKey2 = BouncyCastlePemUtils.readPKCS8PrivateKeySecondApproach(pemFile);
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assertEquals("PKCS#8", privateKey1.getFormat());
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assertEquals("RSA", privateKey1.getAlgorithm());
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assertEquals("PKCS#8", privateKey2.getFormat());
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assertEquals("RSA", privateKey2.getAlgorithm());
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}
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}

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