Re: [Trustedjava-support] Certification of the public keys with the TcIRsaKey.certifyKey() method

[Martin P. <Mar...@ia...>]

Hi...

Maksim Djackov wrote:
> - How can I verify the result of TcIRsaKey.certifyKey() (certify the
> BIND public key with the AIK private key) command on the other machine,
> given the AIK public key and the BIND public key?


The signature verification stuff works about like this...
(from memory, not tested, may be buggy)


TPM machine:

 TcTssValidation certifyResult = bindKey.certifyKey(identityKey, ....);

 ... = certifyResult.getData();            // plain data
 ... = certifyResult.getValidationData();  // signature


 TcBlobData pubBlob = identitykey.getAttribData(TcTssDefines.TSS_TSPATTRIB_KEY_BLOB, TcTssDefines.TSS_TSPATTRIB_KEYBLOB_PUBLIC_KEY);
 TcTcpaPubkey pubStruct = new TcTcpaPubkey(pubBlob);
 ... = pubStruct.getPubKey().getKey();     // public key


Verifier side:

 byte[] aikPubBytes,
 byte[] signatureBytes,
 byte[] plainDataBytes,

 TcBlobData pubKeyBlob = TcBlobData.newByteArray(aikPubBytes);
 TcBlobData certifySignature = TcBlobData.newByteArray(signatureBytes);
 TcBlobData plainData = TcBlobData.newByteArray(plainDataBytes);

 pubKeyBlob.prepend(TcBlobData.newBYTE(((byte) 0)));  // BigInteger requires a leading sign-byte
 RSAPublicKeySpec pubEkSpec = new RSAPublicKeySpec(new BigInteger(pubKeyBlob.asByteArray()),new BigInteger("65537")); // 65537 is TPM default
 RSAPublicKey pubKeyJava = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(pubEkSpec);


 TcIContext context = new TcTssLocalCallFactory().newContextObject();
 // do not connect context, we need no TPM (only possible with IAIK stack)

 TcTpmPubkey pubAikStruct = TcCrypto.pubJavaToTpmKey(pubKeyJava);
 TcIRsaKey pubAik = context.createRsaKeyObject(TcTssConstants.TSS_KEY_EMPTY_KEY);
 pubAik.setAttribData(TcTssConstants.TSS_TSPATTRIB_KEY_BLOB, TcTssConstants.TSS_TSPATTRIB_KEYBLOB_PUBLIC_KEY, pubAikStruct.getEncoded());

 // hmmm... maybe not needed, already set by pubJavaToTpmKey?
 pubAik.setAttribUint32(TcTssConstants.TSS_TSPATTRIB_KEY_INFO, TcTssConstants.TSS_TSPATTRIB_KEYINFO_ENCSCHEME, TcTssConstants.TSS_ES_NONE);
 pubAik.setAttribUint32(TcTssConstants.TSS_TSPATTRIB_KEY_INFO, TcTssConstants.TSS_TSPATTRIB_KEYINFO_SIGSCHEME, TcTssConstants.TSS_SS_RSASSAPKCS1V15_SHA1);

 // do signature verify
 TcIHash hash = context.createHashObject(TcTssConstants.TSS_HASH_SHA1);
 hash.setHashValue(certifySignature.sha1());
 hash.verifySignature(plainData, pubAik);


TODO: check actual content CERTIFY_INFO if as expected


> However, I have another question now as well. This is regarding using
> the public portion of the key created in the TPM to encrypt information
> on another machine and decrypt information later on the TPM where the
> key was created using the private portion of the key.

Errr... I don't think I've ever thought about that...

HTH,
Martin