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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31
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1k views

Does hashing a file from an unsigned website give a false sense of security?

Consider this. Many websites with software downloads also make available MD5 or SHA1 hashes, for users to verify the integrity of the downloaded files. However, few of these sites actually use HTTPS ...
36
votes
2answers
7k views

Why are hand-written signatures still so commonly used?

Why are hand-written signatures still so commonly used? Can they actually prove anything? Two assumptions: If anyone wants to forge my signature I'm sure they will be able to do it. Even my own ...
0
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1answer
79 views

Algorithms for transaction authentication

It's unclear to me how transaction signing and transaction authentication work. Industrial solutions use both symmetric and asymmetric algorithms to compute the signature. What does RSA add the ...
2
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1answer
76 views

Are there theoretical attacks against ECC Digital Signatures?

I was asked to do a research about attacks on various digital signature schemes. There is one thing that bothers me for which I could not find a direct answer. For digital signatures that are based ...
6
votes
3answers
745 views

How can I prove that I wrote a certain blog post?

I would like to be able to prove that I wrote the article that resides at a given URL on someone else's blog. Is there a way that I can do this with public key cryptography? I know a bit about the ...
0
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2answers
158 views

SHA1 - S/MIME and CRL validity after deprecation?

In an internal PKI using SHA1 for hashing, will S/MIME signature and CRL/ARL signature be considered invalid in the next few years (SHA1 Deprecation) ? End certificates can be revoked, CA ...
0
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2answers
74 views

Certificates - What about signing again Intermediate CA certificates?

I an thinking about this issue and it is hard to estimate technical impacts. For any relevant reasons, one want to modify one the x509 field of an intermediate CA. This intermediate CA was signed by ...
0
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2answers
609 views

Encrypt files on FTP server

I have a practical situation here, my company is a FTP server provider for some clients. The clients are sharing their files on our FTP server and have had no problem with access management and ...
0
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1answer
117 views

PKI - Security concerns when changing a certificate hash algorithm

Suppose I want to change the hash algorithm used for a certificate signature (ex: SHA1 to SHA2). Is it better to revoke the previous certificate and issue a new one with expected hash algorithm ? Or ...
1
vote
1answer
401 views

Is there a way to verify a signed XML in Java

.NET has this great way to sign and then verify the signature of an XML file. Is there a way in Java to verify an XML file that .NET has signed this way? thanks - dave
-2
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2answers
60 views

TLS - Are signatures still needed?

The story: I'm currently writing a web service that allows for communications to be made remotely via TCP/IP. I first thought about signing each packet using HMAC-SHA1 with a password, appending the ...
1
vote
1answer
149 views

Algorithm to Transaction Data Signing

Transaction Data Signing I need an idea to develop a very secure algorithm to authenticate online operations using PHP in the server and an Android app in the user's device. What is the idea? The ...
3
votes
1answer
104 views

What is 0xXXXXXXXX.asc.sig and how can I generate this?

When I am exchanging PGP keys with someone, I receive the regular 0xXXXXXXXX.asc file and regularly receive a file called 0xXXXXXXXX.asc.sig. What is this file? How can I generate one and send it ...
1
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1answer
138 views

Use of safe prime in RSA digital signature scheme

For the RSA digital signature scheme , Alice has a pair of public and private keys as denoted by Public key : (e,n) Private key : (d,n) Assuming Alice wants to send a message M to Bob , she would ...
1
vote
1answer
105 views

Using salt or secret for Hmac

I'm working on a web API. We are going to use Hmac256 for signature hashing. From what I can gather, the secret is a key used to initialize the hash algorithm (ie to generate a random number). The ...
1
vote
1answer
83 views

What happens if my signing subkeys are compromised?

Let's say my subkeys are compromised, but my master keypair is safe and secure, so I revoke the old subkeys and issue new ones. With encryption keys, the results are pretty clear: I can still decrypt ...
4
votes
1answer
2k views

Can Fiddler decrypt HTTPS traffic when using elliptic curves + client cert authetication?

Case 1 involves TLS + client certificate authentication with both client and server using secp384 based EC certificates. In this case, when monitoring traffic via fiddler, the tunneling/handshaking as ...
1
vote
1answer
76 views

Would it be possible to verify ownership of digital currency without a network connection to an authority server?

Lets imagine the Fed start registering digital USD for use in offline e-wallets, and they figure out a way to make it so that only registered wallets can make transactions. Without an online ...
2
votes
1answer
127 views

Why are PGP signatures not more widely used as an authentication method?

Example: Bob generates a key pair for this example. Bob registers at example dot com where he provides his public key. When Bob will try to log in, example dot com will ask him to sign a random ...
0
votes
1answer
45 views

What are valid OpenPGP revocation signature types?

I'm working on an analysis of the full OpenPGP keyring (ca. 3.8 million keys). I imported all keys to a local instance of hockeypuck (keyserver implemented in go). Hockeypuck uses a PostgreSQL ...
2
votes
2answers
148 views

Code Signing Confusion

I usually make free windows applications, now I want to digitally sign them. So users can be sure that its from me. But instead of buying the code signing certificate, I thought I may create my own. ...
0
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1answer
122 views

Understanding Digital Signature

I have just learned Digital Signature and am trying to ensure that I have got my understanding of Digital Signature on the correct track. Assume Alice wants to send a message (M) to Bob where the ...
2
votes
2answers
698 views

What agency digitally signed Cryptowall 2.0 so that it can run without being detected?

What agency issued a digital signature for the Cryptowall 2.0 ransomware virus? Is it too early to tell? As far as I know this is how Microsoft planned to prevent malware, by adding a digital ...
0
votes
2answers
100 views

is Digital Signature vulnerable on the Internet?

We all know about how Digital Signing works. I just have some questions about vulnerability risk. At first, As I know, the Signature and the Data are separated and we can split the document into two ...
6
votes
1answer
414 views

How do systems protect against a stolen code-signing certificate after the certificate expires?

Imagine this scenario: 1st December 2014 - a certificate is stolen and used to sign malware with 2014-12-01 timestamp. 15th December 2014 - the certificate is revoked. Malware will be prevented from ...
14
votes
2answers
985 views

How safe are signed git tags? Only as safe as SHA-1 or somehow safer?

How safe are signed git tags? Especially because git uses SHA-1. There is contradictory information around. So if one verifies a git tag (git tag -v tagname), then checksouts the tag, and checks that ...
2
votes
1answer
113 views

What does verified file in windows mean? And does it guarantee related files?

Often when I run a .exe file in Windows, a small box pops up that shows that file is from a verified publisher (e.g Microsoft) or in other case, unknown publisher. I know public key encryption can ...
0
votes
3answers
154 views

Adding a “comment” to PGP mail signature files?

I have started signing my mail with PGP, and it attaches the file signature.asc to my messages to verify that I sent them with content, as you'd expect, like this: -----BEGIN PGP SIGNATURE----- ...
2
votes
1answer
121 views

Is there any asymmetric scheme provides signature with length of 30 bytes?

I want to send short messages to cell phones.Commonly a short message is no longer than 70 bytes. I need 20 bytes or more holding information and the rest bytes are for signature provided by ...
3
votes
3answers
165 views

What are you saying when you sign a PGP key?

When you sign a PGP/GPG key, what exactly are you saying to everyone who sees your signature? Are you validating the person, or the email address? To explain what I mean, take the following two ...
0
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0answers
21 views

Does this show the proper results for signing an XML file

I did the following use this (sign) and this (verify) example on MSDN. Here are the results of all this (don't worry, I will delete the below key and generate new keys, on a different system); XML ...
3
votes
1answer
142 views

Will PGP signed email be blocked in China?

I generally sign all of my outgoing email with PGP. I don't usually encrypt it because most people I send mail to don't have a public key. Anyway, if I send an unencrypted message with a PGP signature ...
2
votes
2answers
500 views

PGP/GPG verifying authenticity

My boss recently implemented a new security system related to PGP/GPG. The whole idea behind this is to sign files so that people know from who they came. They don't require us to encrypt them, just ...
1
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0answers
63 views

Verifying the owner of a signing key

I'm using elliptic curve cryptography (curve25519 and ed25519) for key exchange and signing. The signing and key exchange keypairs are independent. I need two users to be able to verify each other's ...
2
votes
3answers
197 views

Why are apps signed?

From the Android website: Android requires that all apps be digitally signed with a certificate before they can be installed. The signature ensures that only the original developer can publish ...
0
votes
0answers
325 views

Application Privilege Control in Kaspersky blocks program with no digital signature

I made a small application that displays hello world to the console output and attempted to open it in another computer that had Kaspersky fully updated. When I ran the application, Kaspersky gave a ...
0
votes
0answers
25 views

Installer digital signature timestamp inconsistency

I just noticed that the digital signature on an old installer EXE is expired (it's LibreOffice from May 2013, and I'm pretty sure it was valid when I installed it). Investigating further, the time ...
3
votes
2answers
454 views

Why is a CSR hashed?

What are the use cases for defining something other than the default SHA1 hash in a CSR? Is it to protect the digital signature, public/private keys? What is it protecting exactly?
1
vote
2answers
178 views

Are digital signature algorithms subject to the same types of attack as public-key encryption algorithms?

I understand that digital signatures are usually implemented by encrypting a message digest with a private key, decrypting the resulting signature with a public key, and verifying that the message ...
2
votes
1answer
125 views

IKEv2: Why is it important “that each side sign the other side's nonce”

I am currently diging deep into the IKEv2 protocol. In the description of the Authentication (RFC5996, p. 48), the following statement is given: "It is critical to the security of the exchange that ...
4
votes
2answers
827 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 ...
1
vote
2answers
141 views

Is it Possible to use one commercial SSL Certificate to issue end user certs?

My organization is preparing to purchase some 50 "units" from Symantec, with which we can purchase Verisign SSL certificates of varying authentication levels. Our organization does not have--but ...
0
votes
3answers
236 views

Digital Signature and man-in-the-middle

While reading this page about Public-Private key encryption, I asked myself a question about digital signature: Alice wants to sign a message for Bob; she uses her private key to sign the message. ...
0
votes
1answer
176 views

EAP-TLS fragmentation implementation

I am trying to build an EAP-TLS client. The handshake I have to deal with involves receipt of fragmented messages from the RADIUS server. As a part of the client reply, I have to construct a ...
0
votes
1answer
608 views

PDF Digital Signature [closed]

I got free certificate from Comodo and installed on my Windows. Now I'm trying to sign PDF document using this certificate, but get message: "signature validity is unknown": Why is this? How I can ...
0
votes
1answer
300 views

Testing Digital Signature Verification

I'm testing a system which involves updating a database using files sent from external parties. These files sent from external parties are basically just large flat files to update a database. The ...
2
votes
2answers
193 views

Does SMIME differ from TLS, PGP, DMARC signature, or a Portal Encrypted email message in terms of legal non-repudiation?

I'm interested in protecting email messages from NSA-style snooping, but don't want to incur additional legal risk in doing so. In other words, does SMIME encryption and/or signing cause a given ...
-4
votes
1answer
74 views

Digitally sign all outbound data [closed]

I want to digitally sign all outbound data from my computer. Can someone suggest a way to do this programatically or using some tool? Instead of actually signing the data, I would simply append a ...
0
votes
2answers
329 views

Clarifying MITM attacks and Digital Certificate requirement

We are running a Portal application for our client with Payment Gateway integrated. Payment gateway uses SSL as it is suppose to be . The concern for me is that our Portal application does not use ...
0
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1answer
81 views

Digitally sign all the packets from client machine

If I insist on digitally signing all outgoing packets from my computer, would it affect my browsing experience? I mean if a website doesn't expect me to sign my packets, and still I sign them, can I ...