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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Combinations of key exchange and signature algorithm in TLS

Let's say that one does not trust ECC a lot, and values confidentiality over authenticity (perhaps simply for the reason that MitM is more difficult than passive eavesdropping and decryption later ...
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Verifying cryptographically signed files when the key has been revoked

This is mostly a question out of idle curiousity. If I use my private key to sign a file today, forming a signature, and distribute that signature with the document to someone they can then use my ...
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Confidentiality in Digital Signature

Recently I have been working on Digital Signature. Some common reasons for applying a Digital signature to communications are Authentication, Integrity and Non-repudiation. Does Digital Signature also ...
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30 views

Is there a way to sign a 624 bits message on 256 bits

I'm looking for a way to sign a 624 bits message on 256bits (sig length = 256 bits) with an asymmetric keys system? I'm trying to sign a qrcode so a client can be sure that this qrcode has been ...
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51 views

Difference between public key and private key validity period

In the section about certificate extensions, the ITU-T X.509 recommendation writes: The private key corresponding to a certified public key is typically used over a different period from the ...
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132 views

Is it a safe to hardcode my secret key in my iOS app?

Cloudinary iOS SDK configuration suggests to hardcode your api_secret in your iOS app's source code. Isn't that a security vulnerability since string literals can be extracted from the app binary, ...
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Can an embedded CRL be trusted?

Embedding CRLs in a signed document will allow the signature to be validated "long term", by providing a snapshot of the signer's state the moment the document was signed. Im wondering if these ...
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53 views

How can I sign an rpm package using a smart card?

I have a smart card (not OpenPGP card), and I am preparing to sign an rpm using this card. After signing, I will get two files: my.rpm.sig, and my_id.cer. How can I sign my rpm using these extra ...
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Are there any meta-formats for crypto?

Are there are any (properly specified) meta-formats / schema formats for describing cryptographic message structures? I'm looking for a way to describe the format (where some channels might want ...
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58 views

Getting the DNS root name servers in a secure way

It doesn't happen often that a root name server changes, but when it does sometimes it takes months for OS vendors to provide patches and in the mean time there is a security risk. So: How to get ...
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66 views

PKCS#1-1.5 encoding - is there a reason to use 00 in block type?

For encryption block looking like this: EB = 00 || BT || PS || 00 || Data where BT - block type and PS - padding string, I've read that we use three types of BT - 00, 01, 02. Now, since 00 and 01 are ...
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62 views

Man in the middle attack on browser downloads

I'm writing this post from chrome. If I go to a HTTPS site after this, the public keys built into the version of chrome I'm using will be used to verify the site's signature (unless I misunderstand). ...
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65 views

Request signing for REST API

I am building a REST API that will receive requests like: GET /api/entities GET /api/entities?filter=X&sort=Y This seems straight forward: have the client HMAC(path + query, key), send me a key ...
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CMS/PKCS#7: specifying signatureAlgorithm with digest?

I'm confused about algorithm selection for Cryptographic Message Syntax (a.k.a. CMS, PKCS#7) signed objects (RFC5652 Section 5.1). The SignerInfo structure (RFC5652 Section 5.3) has two separate ...
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53 views

Is the enforcement of only allowing signed application to run in a Windows server a safe rule in a prod environment?

There are various security tools that allow an administrator to enforce only signed applications to run in a Windows operating system. is this a realistic general enforcement rule in a production ...
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34 views

Signing (HMAC) cookie identifier

Related to this other question about sharing the secret to sign the cookies, my question is more trivial: how really secure is to sign a simple cookie identifier? In example, expressjs#session ...
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How are digital certificates compared?

I have read about SSL and TLS; I know how RSA works and why digital certificates are necessary (more or less), but I am curious about how we prevent a fake digital certificate. The operating system ...
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30 views

Asymmetric Encryption Digital Signatures

Here is the paragraph I can't quite get my head around. Alice sends a message to Bob and wants him to be sure the message has come from her. • She publishes her public key. • She computes ...
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59 views

RSA vs DSA Digital Signature Message Digest Recovery

I'm learning about signatures using RSA and DSA, I've come across this little fact: RSA can recover the message digest from the signature, whereas in DSA this isn’t possible – you have to have the ...
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57 views

Is a handwritten scanned signature equivalent to its paper counterpart? [closed]

In terms of Authentication, Integrity and non-repudiation, is a handwritten scanned signature equivalent to its paper counterpart? For example, if you have a paper contract and you obtain a digital ...
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How to verify installed packages [closed]

On Linux (Debian x64) I recently installed some software with: apt-get install the_package_name APT told me some packages couldn't be authenticated but I ignored the warning and installed anyway. ...
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80 views

Can a signed downloaded file be securely verified if you only control the private key and the download/verification algorithm?

I'm designing the update procedure for IP Camera's. I'm wondering if my current design is secure enough. I have a binary file that I want to get to a device. I make a hash of this binary file and ...
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Is it possible and does it make sense to sign an E-mail with PGP and S/MIME?

After some research without any answer to my question, if it's possible and does it make sense to sign an E-mail with PGP and s/mime (?), I'm hoping to get an answer here. I know that, PGP and S/MIME ...
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70 views

How do I verify a GPG signature attached for a cleartext email using the gpg command line?

I received an email in cleartext from someone with a signature.asc attached. Looking at the raw source for the email, it was sent with Apple Mail + GPGMail. Reading the message in Thunderbird + ...
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69 views

Use the server's key to digitally sign the HTML content it delivered?

Is there any way to prove that a HTML page was delivered to my browser, and not modified in any way, after it was delivered over TLS? I need to prove integrity, and authenticity of the sender, ...
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143 views

Generating secret keys with secret keys

Hydra is a secretive organization. It is comprised of several Directors at the top, and many Agents underneath them. A Director sends Agents on secret missions. During these missions, communication ...
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PKCS#7 signed data structure in signed PDF document

Is it mandatory to include PKCS#7 data (OID 1.2.840.113549.1.7.1) octet string into the sequence of PKCS#7 signed data? I mean if you want to sign PDF, you are basically adding PKCS#7 container ...
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Signing the Recovery Partition

Do any computer manufacturers sign (DSA, or just publishing a hash) their recovery partitions so that I can be sure that these bits are authentic? I'd like to buy a second-hand computer and reduce ...
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48 views

Subject verification of certificates

Suppose H has taken C’s certificate and manually changed the subject information in C’s certificate from C to H. Would this modification be detected by A during the certificate verification process?
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Untraceable Digital Cash?

I have read some articles regarding digital cash that is untraceable (Here). Their protocol is provided below Withdrawal: Alice creates an electronic coin and blinds it. Alice sends the ...
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Is HTTPS required for PCI Compliance when downloading desktop software patches, if no PII is transmitted, and content is digitally signed + verified?

We have a desktop app that downloads patch content via HTTP. The content is digitally signed and verified by client software after download. Is HTTPS required to achieve PCI compliance if: No PII ...
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120 views

Standard to represent digital signature on paper

Users are making a deal using the website. Website generated PDF file (something like contract or report). Users perform digital signing of this file (analogous to hand-written signature on paper ...
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45 views

Advantage of Group signing over single signing

As i known signing is used to ensure integrity and authenticity of sender. What is the advantage of group digital signing over individual signing. Can anyone explain using a scenario?
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Is LTV in a pdf required if it has a trusted timestamp and the Verification Authority is guaranteed to remain active? [closed]

I have successfully managed to add valid "qualified digital signatures" using a USB token to the PDFs generated by our web application through TCPDF. I am now wondering if I should try to add a ...
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Does a browser have to make multiple requests to verify an SSL certificate chain?

I've learned that SSL certificates can be chained, and the browser will use the issuer's public key to verify the issuer's signature. I have read this article, which has a very helpful diagram, but it ...
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Does PKCS #7 (CMS) add assurance to an email if a CRL/OCSP response is included, then revoked?

Suppose I issue a signing certificate in January, and have a daily CRL issued (expires in 1 day) to verify the validity of that signature. Then sometime in July I need to revoke that certificate. My ...
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81 views

Diffie Hellman and exchange of public key for signature

Let's assume an insecure channel. Is it safe to exchange Alice & Bob public keys first then apply them to sign communications during the DH process? (then encrypt+sign all future communications)? ...
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111 views

how to extract a valid digital certificate and put it on other program

I am working on this matter as a graduate, but I need some help. how can extract a valid digital certificate to put it on other program? can I put a digital certificate on other executables and be ...
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68 views

Can a Bitcoin miner generate SHA2 hashes on arbitrary data?

I'm not asking about bitcoin's design...but am interested in the hashing capacity of a bitcoin miner. To be short: do bitcoin miners(or some of them) accept customizable inputs and hash them in ...
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82 views

multiple authenticode signatures

Is it possible to have multiple Authenticode signatures in an executable? The Digital Signatures tab suggests you can, so I was wondering if, for example, you can sign an executable with Verisign's ...
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Can CA issue a certificate without CSR?

My question is if the CA can generate a private/public keypair on behalf of the requestor and sign it with its own private key? Is there any standard way or protocol to distribute such a ...
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124 views

Rest WebService with signed requests in Java

I'm currently implementing a rest web service with Spring+Java+Tomcat and a cmd client to access it. The most important requirement is to restrict the usage to authenticated users - encryption isn't ...
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Using digital certificates in digital signatures

Please could anybody explain to me how certificates are used with digital signatures? I understand difference between certificates and signatures. It is clear. Digital certificates are used to ...
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39 views

Mail Signing Certificate – What are the impacts when revocated?

Suppose I open a signed mail on 1st January 2000, signature is OK. What about this two cases : 1) If next CRL is to be published one week later, I found it strange that it is “probably” valid until ...
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40 views

What is the ideal HMAC message format if message is an array?

I'm using HMAC exactly as intended to verify the integrity of a message. However, the message is really an associative array (or a hash). Since this will be done on various platforms (within and ...
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63 views

Keeping signatures valid even after the private key has been compromised

If I understand the topic of digital signatures correctly, you sign a message via hashing+encrypting it using your private key. Then, if a private key is compromised by an attacker, she could sign ...
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46 views

Guidance on Login using Digital Signature DSC (PKCS12 and x509 certificate)

I'm interesting in exploring possibility to authenticate user using their Digital Certificate. The methodology is to first register the DSC from the user and keep their Public key along with Serial ...
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90 views

Signature scheme using RSA and SHA512

What do you think about this signature scheme using RSA with 4096 bit keys? Being R pseudorandom padding, fixed length (4096 - 512 bits): RSApriv(R || SHA512(M)) I know that it's not as secure as ...
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Sign java jars for security [closed]

We have an enterprise system that utilizes many in house jars, java applications, to run on a centos 7 linux system. How do I go about achieving the following in order of importance: Only signed ...
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Digital signatures and weak hash functions

There was this question in last year's exam. The teacher claims that answer b) (in boldface below) is correct. Attacks are constantly being performed on digital signatures which use weak hash ...