A digital signature (not to be confused with a digital certificate) is an electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is ...
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Why are hand-written signatures still so commonly used?
I apologize, that this is not an IT security question (at least not directly), but I couldn't find a more suitable StackExchange site to ask this question.
Why are hand-written signatures still so ...
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4answers
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How to achieve non-repudiation?
If I have a message that I need to send to another person, how do I achieve non repudiation ?
Is digitally signing the message sufficient ?
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3answers
4k views
Why should one not use the same asymmetric key for encryption as they do for signing?
In an answer to a question about RSA and PGP, PulpSpy noted this:
It is possible to generate an RSA key pair using GPG (for both encryption and signing -- you should not use the same key for ...
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9answers
598 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 ...
15
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3answers
401 views
What is gained by hashing the last block on-device?
Recently I encountered the notion of "hashing the last block on-device".
It means that when computing a digital signature, the hash that serves as input for the actual signature computation is not to ...
13
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7answers
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Why do people still use/recommend MD5 if it is cracked since 1996?
It's still commonly recommended way of hashing passwords, even if it's insecurity had been proven in 1996
Therefore we suggest that in the future MD5 should no longer be implemented in ...
13
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6answers
788 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 ...
13
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2answers
602 views
Digital Certificate deployment: using two certs for each user?
At a large enterprise environment I have come across a deployment approach for Digital Certificates where each user is issued two (2) key pairs:
One for signing documents, emails, etc. that is ...
13
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4answers
4k views
how digital signature verification process works
I am not able to understand that how the digital signature is verified. I know that digital signature will be attached to the message and sent by sender to receiver. then receiver uses the public key ...
12
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2answers
332 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 ...
11
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1answer
272 views
What are the problems with encrypted but unsigned data?
In another question's answer, D.W. wrote:
Make sure there is authenticity protection for the encrypted data (e.g., encrypt and then sign/MAC): you will need both confidentiality and authenticity ...
9
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2answers
591 views
Does my PGP key really need to match the e-mail address for which I'll be using it?
In considering whether or not I want to join the big web o' trust and put my keys on a key server, I got to thinking about how it would affect my e-mail address' exposure. I generally try to keep my ...
8
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3answers
450 views
Most widespread use of PGP after 20 years
Phil Zimmerman released PGP (Pretty Good Privacy) on June 5, 1991. As we examine the legacy of that far-sighted and brave act 20 years later, what are the most widespread and helpful uses of PGP ...
8
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3answers
291 views
Can signing too much compromise a private key?
Can a collection of many messages signed with the same private key be abused to either forge signatures so some (but not all possible) messages, or even worse to reconstruct that private key with less ...
7
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4answers
1k views
when people say a file has a checked md5 hash, what exactly does that mean?
ok I was just reading this site: http://www.zdnet.com/blog/bott/stay-safe-online-5-secrets-every-pc-and-mac-owner-should-know/3542?pg=4&tag=mantle_skin;content
and thought of something I always ...
7
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4answers
452 views
What good, standard digital signature verification clients are widely or easily deployed?
I'm looking for a good way to publish data along with a digital signature (and ideally a timestamp) which is as easy as possible to verify.
For example, imagine an election administrator who wants to ...
7
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7answers
208 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 ...
6
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4answers
4k views
License key / Serial number generator and checker
I need a serial number generator and accompanying checker. I would like to be able to set a salt (and maybe a length). The generator should only produce serial numbers that pass the test of the ...
6
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5answers
3k views
What does “key with length of x bits” mean?
I'd like to know what it means to say "the cryptosystem C uses keys with a length of x bits". I do not understand what the bits length means... doesn't it depend on the encoding? The same word encodes ...
6
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1answer
3k views
What is the actual value of a certificate fingerprint?
In a x509 digital certificate there is a "certificate fingerprint" section. It contains md5, sha1 and sha256. How are these obtained, and during the SSL connection, how are these values checked for?
6
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1answer
146 views
How to Get and Set Digital Signatures with FDA 21 CFR Part 11 Standards
How do I get and set digital signatures with the 21 CFR part 11 standards as defined by the Food&Drug Administration of the USA?
6
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1answer
534 views
Public key length
I was wondering if there was (and I hope there is) a standard for public key size for ECDH (Elliptic Curve Diffie-Hellman) and ECDSA (Elliptic Curve Digital Signature Algorithm) for every curve type ...
5
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3answers
918 views
Can I use a private key as a public key and vice versa?
I have code to encrypt data using a public key and decrypt it using a private key. This is useful when a client wants to send data to a server and know that only the server can decrypt it.
But say I ...
5
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4answers
3k views
How do the processes for digital certificates, signatures and ssl work?
I have been trying to understand how ssl works. Instead of Alice and Bob, lets consider client and server communication.
Server has a digital certificate acquired from a CA. It also has public and ...
5
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3answers
407 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 ...
5
votes
3answers
250 views
DHE exchange and client authentication
If a server has a known public key and a Diffie-Helman exchange is performed and signed by that key, is there any benefit to authenticating the client before establishing a secure channel instead of ...
5
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5answers
196 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 ...
5
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3answers
251 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 ...
5
votes
1answer
202 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 ...
5
votes
1answer
289 views
OpenPGP Encryption / Decryption Process Using GnuPG
I want to know if my method of encryption can ensure the security of my data if my database was hacked as well as the authenticity of the data I am decrypting. I am using GnuPG's implementation of the ...
5
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2answers
331 views
Enforce Code/Script Signing
I have both a couple of X.509 Code Signing certificates and a GPG keypair that I can use to sign against code I run on my VPS. Every now and again I write code for iOS, OS X and Windows and always ...
5
votes
2answers
1k views
Dealing with expired or revoked signing certificates with Infopath documents
Suppose I have an Infopath form that is digitally signed today by a valid, and active user.
When that user leaves the company, we disable the account and revoke the certificate. This causes a problem ...
5
votes
3answers
76 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 ...
5
votes
1answer
6k views
PKCS7 encoding in Java without external libs like BouncyCastle etc
I am working on signing and encoding of CMS/PKCS#7 messages (something similar to C# SignedCms).
I have x509certificate from the keystore, rsa private key,
ContentInfo. ContentType is "oidPkcs7Data".
...
4
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3answers
590 views
Is there a way to accept signed requests without storing client's password in plaintext?
We are developing REST Web service. We will give Identifier and Secret string to each of our REST clients. When doing requests, clients will authenticate themselves using HMAC algorithm (they will ...
4
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2answers
122 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 ...
4
votes
2answers
809 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 ...
4
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1answer
171 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 ...
4
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1answer
96 views
Are the SSL Digital Security Certifiactes based on Kerberos Network Security Protocol
I just want to know if digital certificates use the kerberos session key algorithm.
4
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1answer
57 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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1answer
51 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.
...
4
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1answer
2k views
openssl verify signature
For S/MIME, I now know I can verify PKCS#7 detached signatures with:
openssl smime -verify -in detachedsign.pem -content content.txt
But what about non-MIME messages?
So if I sign the message ...
3
votes
5answers
184 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 ...
3
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2answers
166 views
Null content digitally signed message
IA technical specification I'm following requires me to send:
The Digital Signature must be in the form of a null content Digitally
Signed message (i.e. a PKCS#7 object containing the signature ...
3
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2answers
160 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. ...
3
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1answer
66 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?
3
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2answers
165 views
security and the well constructed Qt plugin
"All you'd have to do is build a plugin and you could completely pwn the software."
I'm building an application using plugins. I think all you have to do is build a plugin and copy it into the ...
3
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2answers
119 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 ...
3
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2answers
241 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 ...
3
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2answers
1k views
What is the difference between an electronic signature and a digital signature
From Wikipedia:
An electronic signature, or e-signature, is any electronic means
that indicates either that a person adopts the contents of an
electronic message, or more broadly that the ...
