A digital signature (not to be confused with a digital certificate) is an electronic signature that is used to authenticate the identity of a message sender or document signer, and usually to ensure that the original message/document content is unchanged (document integrity).

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How to prevent man-in-the-middle attacks beside of SSL?

I would like to discuss this scenario: There is a HTTPS service which responds with signed keys to an authenticated client. These signed keys can be used for another service to return very sensible ...
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2answers
487 views

Using a Common Private Key for Digital Signatures

I have a mobile application and a server. The mobile application communicates with the server through a web services framework via SSL. The mobile application allows customers to pay for ...
3
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1answer
388 views

GnuPG/KGpg Sign PGP Key - Sign User ID : What is the difference?

What is the difference between signing a user ID and a whole Key ? Which behavior is the best as to signing user IDs and Keys ? How and when to use "Local signatures" (non exportable) ? (I was told ...
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2answers
142 views

Deciding whether to sign someones key

How do i decide whether to sign someones PGP public key? I was looking at some contact pages and they have a request for people to sign their public key. How serious of a commitment is it to sign ...
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2answers
342 views

How do I securely identify a remote (self programmed embedded) device in PHP?

Is there a reliable way in PHP to identify a device that might be behind a Router (so the IP is not unique)? Background: I have several embedded devices (self programmed & adaptable) that contact ...
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2answers
75 views

Which signing strategy?

I have a device which should lock and unlock something after receiving a signed server response. So in the best case a loop would lock like this: User locks device User wants to unlock device User ...
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1answer
572 views

Can you make a digital signature using the receiver's public key?

My question is, can you make a digital signature using the receiver's public key and then have the receiver verify the signature using his private key? I always thought that in order to create a ...
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2answers
102 views

Are there any systems to mitigate the risk of losing a Signing Key?

I want to design a system that hinges on ECDSA. All messages are signed using the algorithm, and this is used to prevent spoofing. However, if a user were to somehow lose control of their key, they ...
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3answers
373 views

Why a self-signed digital certificate (X.509) cannot be altered?

I'm not experienced in code signing but I was thinking about this: as you know, there are various tools for self-signing digital certificate generation (as makecert from Windows or OpenSSL). Now, It ...
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2answers
120 views

Protection of online image file (ancient manuscript) [duplicate]

I am going to protect an image file (ancient manuscript) which will be available online for everyone to download. I want to protect the file in these situations: When it's on the server, I need to ...
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1answer
356 views

Advantages of using a Digital Signature Scheme (DSS) with Appendix instead of DSS giving Message Recovery

I've been looking at the EMV draft specification (pdf) for using Eliptic Curve Cryptography in payment cards instead of the currently used RSA. One thing I've noticed is that they've moved from using ...
2
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1answer
139 views

Licensing/selling digital certificate to another company

I recently stopped distributing my software, so I no longer use the digital certificate (AKA digital signature) I created for it. A couple of days ago, a large software company offered to buy the ...
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1answer
83 views

How can a server recover from its secret key stolen?

Suppose a server use digital signature to prove the files it sends to users. If someone steals the secret key in the server, what should it do?
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3answers
984 views

API message verification without storing private key?

I'm in the process of implementing a public API for my web service. Security is a key concern as money is involved. It seems the current common practice for "authenticating" users in API requests is ...
3
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1answer
124 views

Validate XML-DSig by DVCS

Is it possible to validate an XML message (with XML-DSig or XAdES signature) by a Data Validation and Certification Server (RFC 3029)? Should it understand XML signatures or not? Could it parse XML? ...
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1answer
1k views

How secure is my private key in the Windows Digital Certificate store?

Many files we download don't have digital signatures. Files may get infected or someone may intentionally modify them on our hard disk. So I wrote a simple file hashing program in c# that creates a ...
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5answers
3k views

A standard way to manually add a digital signature to a pdf file?

I've created a few certificates to use myself, but I find myself stumped when it comes to creating a certificate which contains a digital signature. First, how would I go about creating a standard ...
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1answer
921 views

The security of sending emails with SPF/DKIM, but not signed

We're using an email sending service (fairly known) to send our emails. We made DNS changes so that emails going through them would pass SPF and DKIM. A few days ago we noticed that they allow any ...
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1answer
156 views

How do I build a secure signing mechanism on top of HMAC

Say we have a system with strong shared keys (not passphrases), and we're trying to sign messages sent by the server that will be visible to an attacker. E.g. storing session state in a signed cookie. ...
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1answer
73 views

What is closed system esignature?

I need to find a solution for one of my clients who is asking me to implement a esignature solution. I was thinking of suggesting some solutions like DocuSign or EchoSign. But recently my client ...
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1answer
299 views

Where is RSA Digital signature used in the online banking world?

When i do online banking, i sign my digital transaction with a digipass. Ive been told that it uses a RSA-based digital signature scheme. But an rsa digital signature (1024 bit for the modulus) is a ...
7
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2answers
610 views

What asymetric scheme provides the shortest signature, while being secure?

I've had a look at several signature schemes (DSA, ECDSA for the most common ones), and am wondering about whether there exist a scheme that would have the following properties : Be asymmetric (one ...
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1answer
255 views

is pkcs#7 suitable for signing and encrypting zip files?

I'm looking to protect zip files that I will be regularly sending to a 3rd party. I need to ensure strong confidentiality and non-repudation. I would like signing/encryption to be based on ...
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1answer
844 views

how to specify pkcs#7 requirements for a third party you are exchanging data with?

I am looking to use PKCS#7 to sign and encrypt data (offline batch data files) that are exchanged with a 3rd party. I need to write an interface specification for the 3rd party so that they can ...
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4answers
373 views

certificate usage for signing and encryption

I have a question for basic operating with certificates in emails and pdfs. Im familiar with public key cryptography. The scenario: In my scenario I want to send a confidential email to a person A ...
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2answers
726 views

what is the difference between a mac and a digital signiture

I understand that a MAC algorithm takes a message and a private key as input and hashes them to a value. I understand that senders and receivers often use MACs to authenticate a message and check the ...
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1answer
145 views

Does DSA need padding?

So i read on wikipedia that digital signatures need padding (like PSS) and i know this is true for RSA. But know i ask myself does DSA also need padding?
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1answer
355 views

PKCS#7 message constructed by our code, any weaknesses in the output?

We have this as the PKCS#7 encrypted message. We would like to open this up for review and analysis here, for people to poke holes. This sample is generated via test certificates and keys. The concern ...
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1answer
57 views

How esignature verification process work?

I have a web application in which the users will be signing an html report. I know how the digital signature authentication works. But here the user will literally be signing the document (So, Should ...
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3answers
2k views

Is a 512 bit RSA key secure when used temporary?

Is a 512 bit RSA key secure when a new key gets generated and used approximately once a week? The key is only used for signing messages, not for encrypting sensitive data. This is for a system where ...
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2answers
522 views

Does Authenticode still work offline and with a “fake” certificate

Here's our story: We're developing some software (written in C#/.NET) and we're already signing the assemblies with strong names, I do this in Visual Studio with a pfx file that is protected by a ...
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7answers
272 views

Proving running code on a website is unchanged

Can it be proved to the user that the running code behind a website with security related code is the same as published? I'm currently looking at a few new project ideas and one involves secure ...
5
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1answer
280 views

Most efficient key algorithm for a TLS server key?

Let's assume I want to setup a HTTPS service on a modern-but-no-so-speedy x86 server without any form of hardware cryptographic accelerator. Which key algorithm should I choose for the server key in ...
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2answers
3k views

When using symmetric key encryption, do we need to sign?

Say we're using a shared key between two parties, that has been distributed using public key encryption, is it still necessary to sign any data that's encrypted using the shared key? Or is it enough ...
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2answers
405 views

Which factors should I consider for devices that accept handwritten digital signatures?

These days many locations ask you to give your signature on a digital signature pad/device. As I am situated in Europe, the EU directive 1999/93/EC seems to regulate it. From what I have found out ...
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1answer
2k views

Parsing a PKCS7 detached signature hash

I'm trying to manually verify signatures of Apple iOS Passbook files, which are PKCS #7 detached signatures of the RSA key of the Apple developer who created the file. Which means there's a file ...
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1answer
211 views

Is the `ssh-agent`'s DSA signature deterministic?

In my hopes to use ssh-agent to generate a signature as password I implicitly assumed a deterministic signature. DSA is however supposed to take random value k for signing. However that randomness is ...
5
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3answers
484 views

Is piping a `ssh-agent` signed message as a password secure?

There's an encrypted filesystem on a server I ssh into using public key authentication. Since a forwarded ssh-agent can deterministically sign a message (see also the ssh-agent protocol section ...
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1answer
683 views

How to verify the signature in an iOS Passbook pass?

The Passbook application in the new iOS6 keeps track of movie tickets, coupons, and other 'passes' for you, and the passes themselves are loaded onto the user's device via file packages with the ...
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3answers
1k views

rsa encrypted hash == rsa signature

$ echo -n "1327943823" > test_ok.txt $ openssl dgst -sha1 -binary -out test_ok.sha1 test_ok.txt $ echo "GURbsl4CFPCG83RCZxsEpoRleXicXQhH1OC4Fk77b7EMj2g8aHUhD/L+sm ...
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6answers
2k views

Why not RSA-encrypt the entire document?

I have recently learned of a way for person B to verify that a document sent from person A is indeed from person A. Person A gives Person B his public RSA key. This must be done reliably. Person A ...
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2answers
806 views

Revoked certificate validation using past times

I'm working on XAdES implementation for Java, as such I require cryptographic implementation to be able to verify certificates in the past. Unfortunately I have problems verifying revoked ...
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5answers
224 views

Is there any security value of creatively naming folders containing sensitive files?

A friend of mine asked me if he could sign his tax returns without printing them out. While helping him, he insisted on naming the folder containing images of his signature and initials a completely ...
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0answers
203 views

Verifying Authenticode signed executables and DLLs using OpenSSL API [closed]

I have installed openssl and now the rsa_test.c is running fine. What I want to do is: Open any exe or dll digital certificate. Extract the Thumbprint and PublicKey. The public key contains the ...
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2answers
490 views

Distributed XAdES-X and XAdES-A signatures over multiple documents

As the standard is not completely clear in this matter, I'm trying to found out if the XAdES standard (ETSI TS 101 903 v1.4.2) describes distributed case in which the SigAndRefsTimeStamp element or ...
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2answers
155 views

How does a code signing vender charge for creating certificate chains?

I have a question about creating digital signatures for pdf files. I want to have a certificate for my company and have children certificates as many as the number of company's employees who can ...
3
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2answers
275 views

Reusing HMAC state for multiple messages

I have a secret key k and message m. I send m || HMAC(m, k) to some other party, who can verify the integrity of m, assuming that they know k. Suppose I have multiple messages m1, m2, and so on. ...
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3answers
727 views

Digital Signature and Verification?

AFAIK , When Alice wants to write a message to Bob -- she uses Bob's public key and encrypt the message - and then Bob - using his private key - use to decrypt it. So public key is used to decrypt ...
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1answer
77 views

Standards for CA cert revocation and time-constrained cryptographic algorithm parameters

I'm working on software that will be in use for foreseeable future (15 years+) that will need to validate XAdES-A signatures (long term archival, similar to PAdES-A, but for XML). That means, it will ...
4
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2answers
627 views

What are the real-time applications of long term digital signature with timestamp

I want to know the real time applications that uses digital signatures with timestamps. Specially I am interested to know the applications where we can trust an old signed document which is now ...