4

I have gone through many similar threads but no luck!!

I want to generate public and private keys using a PEM file. Following is the code I am using for the same:

        String pemFileNme = "C:\\Users\\amitmm\\Desktop\\clean\\key.pem";

        File pubKeyFile = new File(pemFileNme);
        File privKeyFile = new File(pemFileNme);

        // read public key DER file
        DataInputStream dis = new DataInputStream(new 
        FileInputStream(pubKeyFile));
        byte[] pubKeyBytes = new byte[(int)pubKeyFile.length()];
        dis.readFully(pubKeyBytes);
        dis.close();

        // read private key DER file
        dis = new DataInputStream(new FileInputStream(privKeyFile));
        byte[] privKeyBytes = new byte[(int)privKeyFile.length()];
        dis.read(privKeyBytes);
        dis.close();

        KeyFactory keyFactory = KeyFactory.getInstance("RSA");

        // decode public key
        X509EncodedKeySpec pubSpec = new X509EncodedKeySpec(pubKeyBytes);
        RSAPublicKey pubKey = (RSAPublicKey) 
        keyFactory.generatePublic(pubSpec);

        // decode private key
        PKCS8EncodedKeySpec privSpec = new 
        PKCS8EncodedKeySpec(privKeyBytes);
        RSAPrivateKey privKey = (RSAPrivateKey) 
        keyFactory.generatePrivate(privSpec);

Exception:

Exception in thread "main" java.security.spec.InvalidKeySpecException: 
java.security.InvalidKeyException: invalid key format
at
sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:205)
at java.security.KeyFactory.generatePublic(KeyFactory.java:334)
at main.java.me.txedo.security.Main2.f1(Main2.java:47)
at main.java.me.txedo.security.Main2.main(Main2.java:20)
Caused by: java.security.InvalidKeyException: invalid key format
at sun.security.x509.X509Key.decode(X509Key.java:387)

PEM File Content:

-----BEGIN RSA PRIVATE KEY----- MIIEowIBAAKCAQEAwnEEodFEf86+Ae+wYyI//u1kekIWnA3RfzbAwWD77uG7D9Ci 9vVNbPO4XT2hKL03/q7d7KTgrA1sjBltfaOzVfA56x1S/0cYVk4xI440dpLo0F+m RIqRw5fh8IuUlUIr3I4A7ESkDQQsZbDpdgCiNbrlADqLotcZyB4rU4uURW8QUI/W eqsD6TOQs4bI+3o3xAKkky2kXujSaaa3tDxgUPTmSQ0Buk7Hx/IVzwyV7qjWiR4U C46rHpnWxfF0DWuJUOYgJmBQ8xFOQwt4Ec/u+0m8top8cqQF+gpBn9iLXpbtahA3 pqyvLuNXRH9yn8mlEneBrjjl6U0H3W/AV7/dGwIBAwKCAQEAgaCtwTYtqonUAUp1 l2wqqfOYUYFkaAk2VM8rK5X9SevSCosXT04znffQPikWGyjP/x8+ncNAcrOdsrue U8J3jqAmnL43VNoQOYl2F7Qi+bdF4D/ELbG2gmVBSwe4Y4FykwlV8thtXgLIQ8tG TqsWznyYqtGybI9mhWlyN7Ji2POMDZP5Lwx7M01pMezwpnsZSmPVL9TgVrtWv4xt C0vPyuy9THlFWtkOdHItNK+vOTcpuHn29rFUJI/D3R+SQjcdqj3aaqljOtdeBxgd yDl2/Z4rUyetgzcZMfNTt/NRT0hOJ6R6/2S7gFCTtxMHBh3vVCH+pLLnQyJvcPQu AsORSwKBgQDhOPr1x/8BioqaasoXvO9NsGktCgPDjbC4d3jR8n6lCa42X/eIahaD xi1VGWyQhdO7aMXiDmzOtox7xHcMRh+a5ySIs9gTsHkMB2hqwIUNg25INRkQ3Vr3 eWnoTBGsfJqC1TEME3ocKwmyz57ZAe4yyR/ZRdDX5DUt9qCCFeA8uQKBgQDdAzbq 7BlJkbTYfdlIRNJEJAO3wWqQTx8X0ttCMMwDluOT9l+RR/KuUxl85ph+kwJci6E/ ixfeMTW1NcsMY/lB6mTP0oooalU1MP7gpPSu+24zhLXnUHZotbNbv9nk6w/1WWhz FBt5w2DG4kQPFK6LSySqcVuzIGQyvWD5PbpGcwKBgQCWJfyj2qoBBwcRnIa6ffTe dZtzXAKCXnXQT6XhTFRuBnQkP/pa8WRX2XOOEPMLA+J88IPsCZ3fJF2n2E9dhBUR 722wd+VidaYIBPBHKwNeV57azhC16OdPpkaa3WEdqGcB43YIDPwSx1vMimnmAUl3 ML/mLos6mCNz+cBWuUAoewKBgQCTV3nx8ruGYSM6/pDa2IwtbVfP1kcK32oP4eeB dd1Xue0NTupg2qHJjLuombr/DKw9smt/sg/pdiPOI9yy7VDWnEM1NwbFnDjOIKnr GKMfUkl3rc6aNaRFzneSf+aYnLVOO5r3Yrz715XZ7C1fYx8Hh23G9j0iFZgh05X7 fnwu9wKBgHyC0X26KZQ0ukan5jDSiz4dapUp2d3F+vnRzZa2AOsmo995gsXLdfsJ n0o4Z3LsQJUDRI3tQ4dXe/5jS4oFrOdxALOAw6YmvEv/3oHwsCYPDhqLNfIJ9I6m Dt3yG61pUJiCArhPaYG17NQoCxF6Xi6GUajRsECbr8DdyGMAu5eE -----END RSA PRIVATE KEY-----

I have tried removing file header and footer manually. I tried code from bouncycastle, no luck, same error.

Python code which works with this file:

def t2e_enc(plaintext, pk_pem_file = './2017-12-04T062008Z.pem'):
''' 
Function for encryption of Track2 credit card data.
This function uses private key to derivate public part used for encryption

'''
with open(pk_pem_file, 'rb') as pk:
    private_key = serialization.load_pem_private_key(pk.read(), 
    password=None, backend=default_backend())

public_key = serialization.load_pem_public_key(
    private_key.public_key().public_bytes(
        serialization.Encoding.PEM, 
        serialization.PublicFormat.SubjectPublicKeyInfo),
        backend=default_backend()
    )

ciphertext = public_key.encrypt(
    plaintext,
    padding.OAEP(
        mgf=padding.MGF1(algorithm=hashes.SHA1()),
        algorithm=hashes.SHA1(),
        label=None
    )
)
b64ciphertext=base64.b64encode(ciphertext)
return b64ciphertext

I am doing this for the first time, so bear with me if there is any silly mistake.

halfer
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1 Answers1

7

Partial dupe Load RSA public key from file

So, you 'wrote' (I assume, copied) code that clearly says you need two files, in DER form, containing PKCS8 and 'X509' encodings. (What Java calls X.509 here is really the SubjectPublicKeyInfo component of X.509.) You give it one file, in PEM form not DER, containing a PKCS1 encoding not PKCS8 or X509 -- and you're surprised it doesn't work? Python works because it calls OpenSSL, and OpenSSL supports over a dozen encodings and formats for privatekeys, including this one; Java supports only one (outside of keystores) which isn't this one. (Bare) publickeys are a little better; internally libcrypto supports multiple forms, but in practice only two of them are used, and one of them matches Java -- although many publickeys are distributed, stored, and used in the form of X.509 certificates, which provides several more forms to worry about.

There are approximately 7 solutions to your situation:

  • the simplest is to use OpenSSL commandline to convert your one file to the two files Java wants:

      # (corrected! pkey is inconsistent!) 
  openssl pkcs8 -topk8 -nocrypt -in input.pem -outform der -out private.der

  openssl pkey -in input.pem -pubout -outform der -out public.der
  # or for very old versions (should not be needed now)
  openssl rsa -in input.pem -pubout -outform der -out public.der

    Those files can now be read by the code you posted (except with the filenames separated). Note this conversion doesn't have to be done on the same system; if necessary you can do it elsewhere and copy the files, if you use a method that works for binary files i.e. NOT cut&paste.

  • if you really want only one file, but it can be converted, create the private.der file as above and read it with only the privatekey-related parts of your code, then do:

      RSAPrivateCrtKey priv2 = (RSAPrivateCrtKey)privKey;
  PublicKey pubkey = keyFactory.generatePublic(new RSAPublicKeySpec(priv2.getModulus(), priv2.getPublicExponent()));

  • you could convert the files to PKCS8 and 'X509' PEM by omitting -outform der from the above conversions, then read those files and manually 'de-PEM' by removing the header and trailer lines and converting the base64 to binary (removing or skipping the linebreaks); this results in binary PKCS8 and X509 encodings you can run through your existing code. This is as much work on the openssl side and more work on the Java side so there is no apparent advantage, except that PEM files are valid text and can be cut&pasted if necessary.

  • combining these, you could convert to PKCS8 PEM only, read that per bullet 3 (de-PEM then the privatekey parts of your code), then extract publickey from privatekey per bullet 2

  • one way to use the format you have (unconverted) in plain Java is to de-PEM per bullet 3 giving you a PKCS1 encoding, then manually construct the PKCS8 encoding, then proceed as before to run the PKCS8 through the KeyFactory and extract publickey per bullet 2. See my answer at Java: Convert DKIM private key from RSA to DER for JavaMail for a really ugly way to do this (including one de-PEM method). There is a better way if you use BouncyCastle (which has a class for this ASN.1 type), but if you use BouncyCastle it's better not to use this method at all, see below.

  • another way to use the unconverted format in plain Java is to de-PEM per bullet 3, then parse the ASN.1 structure of PKCS1 and construct an RSAPrivateCrtKeySpec which you can run through your KeyFactory instead of a PKCS8 encoding then extract publickey per bullet 2. This is even more complicated, although I think I have seen it somewhere; will add if I find it. Again BouncyCastle can improve this method, but doesn't need to, see below.

  • finally, if you have BouncyCastle it's dead easy. You don't say what you tried with 'no luck', but the following BouncyCastle code is all you need and does work:

      try( Reader r = new FileReader(filename) ){
    KeyPair pair = new JcaPEMKeyConverter().getKeyPair((PEMKeyPair)new PEMParser(r).readObject());
  }

Note this gives you a KeyPair with both privatekey and publickey objects from the one file.

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