using following code; when i tries to get access the signed from the PKCS7 attached signature.
cms = new CMSSignedData(envelopedData); //PKCS7 envelope
String signedData = new String((byte[])cms.getSignedContent().getContent());
I got the output like this.
nº™(5š?¶ÁNšc«n‘¶˜Êõûøˆ‚<ùæB0¸ð¿ø"˜ZÊ×`—õWøž8¹¨c ¼‘Ç{¥é×Æx¢ôãÕ›|?€çžÆ3ÔÜç&¦¤X„õ·3c'Gž\³Ö/€Á<ž²¬ÿµƒÉâw…«b›¤?¤1®kB•ô?³Á2€¦?r`!¦÷nt¯*Ÿ
Same thing works fine for detached signature. For attached signature, i used the following code.
CMSSignedData sigData = gen.generate(msg, true);
Even. I tried all the charsets for the signedData String.
I found the problem and resolved it. It was due to the double signing process.
Related
The plain text is signed using java.security.Signature. Below is the code used to sign the plain text
public String getSignature(String plainText) throws Exception
{
KeyStore keyStore = loadKeyStore(); // A local method to read the keystore file from file system.
PrivateKey privateKey = (PrivateKey) keyStore.getKey(KEY_ALIAS_IN_KEYSTORE, KEYSTORE_PASSWORD.toCharArray());
Signature privateSignature = Signature.getInstance(SIGNATUREALGO);
privateSignature.initSign(privateKey);
privateSignature.update(plainText.getBytes("UTF-8"));
byte[] signature = privateSignature.sign();
return String.valueOf(signature);
// KEY_ALIAS_IN_KEYSTORE, KEYSTORE_PASSWORD and SIGNATUREALGO are all constant Strings
}
Note 1: I found online a way to verify the signature using the public key Java Code Examples for java.security.Signature#verify(). But this is not what I require.
Note 2: I also found a ways to encrypt and decrypt as mentioned here RSA Signing and Encryption in Java. But the use case I have in hand is to get the original plain text from a signed data. Is that possible?
No, you can't retrieve the original content from just the signature.
The signature alone does not contain enough information to restore the original clear text, no matter what keys you have access to.
The basic idea of a signature is to send it together with the clear text. That means the clear text will be visible, but the signature can be used to verify that the message was written (or at least signed) by who claims to have done so and has not been tampered with since then.
Signing something is different from encrypting it. The two often uses the same or related technologies and both fall under cryptography.
I am trying to add digital signature to pdf document using pdf-box library (v2.0.8). I am receiving already signed content from a webservice (signed with only private key). Now I would need to associate certificate information to this signed data so that it can be added to PDF document. How can we add certificate to already signed content, preferably using bouncy castle api ?
// here content is data which has to be signed
public byte[] sign(InputStream content) throws IOException {
try {
CMSSignedDataGenerator gen = new CMSSignedDataGenerator();
List<Certificate> certList = new ArrayList<Certificate>();
certList.add(certificate);
Store certs = new JcaCertStore(certList);
gen.addCertificates(certs);
CMSProcessableInputStream msg = new CMSProcessableInputStream(signPrivate(content));
CMSSignedData signedData = gen.generate(msg, false);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DEROutputStream dos = new DEROutputStream(baos);
dos.writeObject(signedData.toASN1Structure());
return baos.toByteArray();
} catch (Exception e) {
throw new IOException(e);
}
}
Here, I am able to generate digital signature, but it does not contain any certificate information. I already checked this and this question but they donot take the case where content is already signed using private key seperatly and only certificate needs to be associated.
(The code you posted refers to CMS signature containers, so I assume we are talking about adbe.pkcs7.detached or ETSI.CAdES.detached PDF signatures.)
When creating a signature in a CMS signature container, one has the choice whether the signature value really only signs the (hash of the) document data or whether it signs a collection of so-called signed attributes (signedAttrs in the SignerInfo specification) and the hash of the document data is but a value of one of those attributes.
SignerInfo ::= SEQUENCE {
version CMSVersion,
sid SignerIdentifier,
digestAlgorithm DigestAlgorithmIdentifier,
signedAttrs [0] IMPLICIT SignedAttributes OPTIONAL,
signatureAlgorithm SignatureAlgorithmIdentifier,
signature SignatureValue,
unsignedAttrs [1] IMPLICIT UnsignedAttributes OPTIONAL }
(RFC 5652 section 5.3. SignerInfo Type)
All profiles hereof to be taken seriously, though, require that you use signed attributes, in particular they require you to use an ESS signing-certificate (RFC 2634 section 5.4) or ESS signing-certificate-v2 (RFC 5035 section 3) signed attribute to reference the signer certificate.
In these attributes, therefore, the association of the signature with its signing certificate is fixed before the signature value is generated.
Thus, you cannot freely associate a signing certificate to an already generated signature.
At the moment in C# I'm signing a challenge like this:
RSACryptoServiceProvider rsa;
RSAPKCS1SignatureFormatter RSAFormatter = new RSAPKCS1SignatureFormatter(rsa);
RSAFormatter.SetHashAlgorithm("SHA1");
byte[] SignedHash = RSAFormatter.CreateSignature(paramDataToSign);
Then I give the SignedHash to Windows, it accepts it and everything is OK. But I need to move this part to Android and there's the problem, that I just can't get the same signed hash value.
In Android I tried to make the signed hash but they differ from the one generated in C#.
Signature signer = Signature.getInstance("SHA1withRSA", "BC");
signer.initSign(privateKey);
signer.update(paramDataToSign);
signer.sign();
In C# - using the following piece of code - I get the same result as in Android, but it is not an option cause then Windows does not accept the signed hash.
ISigner signer = SignerUtilities.GetSigner("SHA1withRSA");
signer.Init(true, privateKey);
signer.BlockUpdate(paramDataToSign, 0, paramDataToSign.Length);
signer.GenerateSignature();
Here's written that C# PKCS1SignatureFormatter and Java Signature should give the same result, but they do not. http://www.jensign.com/JavaScience/dotnet/VerifySig/
What could be the problem?
Here are the base 64 (WebSafe) values that I get:
Challenge = zHyz12Tk4m151nssYIBWqBCAxhQ
RSAPKCS1SignatureFormatter SignedHash = kmu39keplCAV4Qnu22wdprLz4nGSsrVtHbxQ5YMUG7p-0YwReCG4ROIlFvYs4CGfjCiAGFPw4PLrLx7mrlAA6iuhJMkgm_PMTW9alQYTH612hLEUP4EmK0M2kw8CveLcjI3HA08z8bByllIzRyAlM8bcR438vw2uhx_CbgvOOHn8vwBPnvWbFqpi2doYoq2xEuFBRe7eBPrxbMRqEd3ExdQ9c9rYT4ivOJ4pbioyi6D5i5_1crvGwM6nQanMZCmooRYJO65NP3B4wWnvQZpJLRD0U08wWcvyGBFWp188ZovDjnkTQZku6lzmwGXfqQwtBz9uNvLcTbp7cVyt5EyQxw
Signature and ISigner SignedHash = Vt-b5QfGPnSPpZuIB8-H4N1K5hQXpImS4e8k56_HruDSqy3DLsz96QKUrccshjr1z9nTK3Mwvd5yPdyTJOqSUcDQqxV46LPhWQNsubqKxAz97ePpeslIH1gHdnzkh46ixsWqgDrhR7egQtDkU8PPsph1qahCxaVkRYspQBV0jPZ-LK4EjoGGnuWTCihVKjruXJZ2VY8yZ9QRAsHVptr0Nv-mldO2MFK-oEVbtVbHqUPf5So8im3oRSm68OqY4g56bCdFNSbhcFBjrZ1QPjnxiIk43-_5tevafqoOB2D_E_mQHCJwmRg3MrNij6IdAdloCejnhCWzgMHdcG1Ug_Qmig
EDIT:
So the simplest solution is using Bouncy Castle API:
AsymmetricBlockCipher rsaEngine = new PKCS1Encoding(new RSABlindedEngine());
rsaEngine.init(true, privateKey);
DigestInfo dInfo = new DigestInfo(new AlgorithmIdentifier(X509ObjectIdentifiers.id_SHA1, DERNull.INSTANCE), paramDataToSign);
byte[] digestInfo = dInfo.getEncoded(ASN1Encoding.DER);
rsaEngine.processBlock(digestInfo, 0, digestInfo.length);
The problem is that RSAFormatter.CreateSignature(paramDataToSign); passes the hash value, while signer.update(paramDataToSign); passes the data before it is hashed. So it is likely that you have to remove a MessageDigest calculation for your Java code for this to work.
Alternatively, if you only have the hash value, you may have a look into the Bouncy Castle lightweight API to find a method that accepts a value that is pre-hashed. This can probably be performed using new RSADigestSigner(new StaticDigest(paramDataToSign, "SHA-1")).generateSignature().
Problem is that StaticDigest does not exist, so you'll have to comment here if you really require it. Alternative, mirror the implementation of RSADigestSigner but substitute a pre-calculated hash.
I am using BouncyCastle to generate a DSA signature but using the native JCE to verify the it.
NOTE: I am working with a j2me client that does not natively support signing hence the need for BouncyCastle)
So, on the client the signature is generated as follows:
DSASigner sig = new DSASigner();
sig.init(true, privateKey);
String plaintext = "This is the message being signed";
BigInteger[] sigArray = sig.generateSignature(plaintext.getBytes());
...
sigArray contains 2 BigIntegers r and s.
This signature then has to be transmitted to a server which uses native JCE to verify the sig. On the server side, using the native Java JCE, it should be possible to verify a signature as follows:
...
Signature sig = Signature.getInstance("SHA1withDSA");
byte[] sigbytes = Base64.decode(signature);
sig.initVerify(publicKey);
sig.update(plaintext.getBytes());
sig.verify(sigbytes)
The problem am having is: how do i encode sigArray into a format that can be sent to the pc/server as a single Base64 string (instead of separately as r and s) that can then be verified on the server using the native JCE method show in the second snippet of code?
So far i have tried to create DERObjects from the r,s arrays (separately, together as one array, encoded) but still no luck. Anybody faced this before? How did you tackle it?
According to Cryptographic Message Syntax Algorithms (RFC 3370) the DSA signature encoding is an ASN.1 sequence containing both integers r and s:
Dss-Sig-Value ::= SEQUENCE {
r INTEGER,
s INTEGER }
I have a signedCMS, and would like to know how to use Bouncy Castle API to remove the signature so I can have clear access to the plain text file underneath?
Thanks
Something like this might work:
CMSSignedData signedData = new CMSSignedData(signedFileBytes);
// Now get the content contained in the CMS EncapsulatedContentInfo
CMSProcessable processable = signedData.getSignedContent();
You should then be able to get a stream on processable from which the data can be read.