Questions tagged [certificates]

A certificate consists of a public key and information about the owner (e. g. the name of a person or server).

Filter by
Sorted by
Tagged with
78 votes
12 answers
16k views

Who verifies the trust of certificate authorities?

Background I am a novice in the field of cryptography and cyber-security, and while studying asymmetric-key encryption, I learned about the potential of a man-in-the-middle attack. To mitigate this ...
user avatar
  • 1,305
37 votes
3 answers
8k views

Does "Shattered" actually show SHA-1-signed certificates are "unsafe"?

Note: I am not advocating anyone continues using SHA1-signed certificates: they are dead as far as security is concerned and should no longer be used. I'm just trying to clarify my understanding of ...
user avatar
28 votes
4 answers
27k views

Recommended skills for a job in cryptology [closed]

First let me apologize if this is an ill posed question. Let me also note that I do not in any way seek a comprehensive answer, simply your thoughts on what makes for a valuable asset to a company ...
user avatar
  • 409
27 votes
2 answers
23k views

Unpredictability of X.509 serial numbers

About X.509 certificates serial numbers the RFC 5280 says: The serial number MUST be a positive integer assigned by the CA to each certificate. It MUST be unique for each certificate issued by a ...
user avatar
  • 491
20 votes
2 answers
43k views

Difference between "Signature Algorithm" and "Signature Hash Algorithm" in X.509

What's the difference between the "Signature Algorithm" and the "Signature Hash Algorithm" found in an X.509 certificate? Why does it need a "Signature Hash Algorithm"? Edit: I'm creating the X.509 ...
user avatar
  • 343
18 votes
1 answer
44k views

Is PKCS7 a signature format or a certificate format?

I always though PKCS7 was a signature format. However, on the net I find several references to PKCS7 being a certificate format - for example, this talks about PKCS7 certificate: Extract raw ...
user avatar
  • 1,678
16 votes
1 answer
1k views

Who issued the first SSL certificate?

When SSL was introduced in ~1996, there was only a few CAs issuing certificates for that specific use and a few sites which actually used SSL. Which Certification Authority issued the first SSL ...
user avatar
  • 785
13 votes
3 answers
6k views

Are there other digital certificate formats than X.509?

Hi I am a little new to security, but in researching digital certificates it seems the only format people describe is X.509. Are there other formats? If so what are they and where can I find ...
user avatar
12 votes
3 answers
4k views

Smallest possible certificate for IoT device

I'm developing an IoT system that uses small nodes connected through RF. This allows messages under 250 bytes long. You can check it at https://github.com/gmag11/EnigmaIOT. All messages are encrypted ...
user avatar
  • 121
12 votes
2 answers
9k views

How does a certificate authority issue a digital certificate?

I am new to cryptography and I want to know the details of how a Certificate Authority issues a digital certificate. From what I know (please correct me if I'm wrong at any parts of my explanation): ...
user avatar
12 votes
4 answers
20k views

How does a client verify a server certificate?

As far as I know, when I request a certificate from Verisign (for example), and after they approved that I is me, they create a certificate (for me) that contains the digital signature and public key. ...
user avatar
11 votes
2 answers
5k views

Why is a CSR signed and which key is used for signing?

I know that a CSR includes a public key from which a signed certificate shall be generated. But why is the CSR istself signed and which key is typically used? For signing I need a private key, so the ...
user avatar
  • 1,427
10 votes
1 answer
5k views

Need an introduction to SPKI (or "SPKI for dummies")

I am familiar with concepts such as the following: PKI and CAs ID based cryptography Certificateless cryptography PGP web of trust more or less anything in basic Crypto that is taught in a college ...
user avatar
  • 1,649
10 votes
1 answer
6k views

Why does the PKCS1 RSA private key structure contain more than just exponent and modulus?

The ASN.1 spec for the PKCS1 RSA private key format is as follows: ...
user avatar
9 votes
2 answers
11k views

What happens when a root CA has its private key compromised?

What happens when a root CA has its private key compromised? Then all children in the tree are compromised too? And then all certificates are compromised? What needs to happen then? Related: - How ...
user avatar
  • 1,213
9 votes
1 answer
7k views

How do other, non-RSA algorithms, compare to the PKCS #1 standard?

Arguably the PKCS suite of standards have a profit-oriented bias as they are promoted by RSA and promote their algorithms over others in the form of RFCs and other means. I'm considering the ...
user avatar
9 votes
4 answers
2k views

Can we design a public-key infrastructure without certificate authorities?

In a recent essay, Bruce Schneier tasks the engineering community with redesigning and rebuilding the vulnerable parts of the Internet's backbone. We need to figure out how to re-engineer the ...
user avatar
  • 4,548
8 votes
2 answers
528 views

Must root certificates be self signed?

Root certificates are normally self-signed. What is the reason behind that convention? I mean, one must trust the root certificate in a non cryptographic way anyhow.
user avatar
7 votes
1 answer
3k views

How is OID 2a 86 48 86 f7 0d parsed as 1.2.840.113549?

I saw that an RSA key, created by OpenSSL, contains the following HEX string: 2a 86 48 86 f7 0d 01 01 01 that HEX string gets interpreted as Object ID: 1.2.840.113549.1.1.1 It is obvious 01 01 ...
user avatar
7 votes
1 answer
9k views

What does "G2" mean when used with X509 certficates and certificate authorities?

For example "Google Internet Authority G2"?. I thought it was another way of specifying Class 2 (for organizations, for which proof of identity is required) but then see certificates such as "VeriSign ...
user avatar
  • 171
6 votes
2 answers
2k views

Do certificates need to be stored as encrypted?

The titles says most of what we're confused with. Here's some details: On an embedded device, we have a microcontroller and external flash memory. This memory can be easily read and written to in ...
user avatar
6 votes
2 answers
5k views

What exactly is inside a private key?

May sound stupid to many, but I would like to have some pointers on what exactly is contained inside a private key. I have decent understanding of public/private keys/certificates (have created them ...
user avatar
6 votes
2 answers
275 views

Is the warning given by chrome warranted?

I went to a payment page on a site recently, and chrome was warning me that the page is possibly not secure, I have a very basic understanding of crypto but not enough to fully understand why this ...
user avatar
  • 163
6 votes
1 answer
2k views

Client and server using same SSL certificate - any issues?

I'm working on software where multiple components will communicate with each other using SSL. There would be one central component acting as a server, which would also require the clients to present ...
user avatar
5 votes
3 answers
2k views

Deduce modulus N from public exponent and encrypted data

This is an RSA question, given data encrypted with a public key from an unknown RSA certificate of 2048 bit, let $X$ be the encrypted data, $M$ the unencrypted data, $c$ the public exponent and $N$ it'...
user avatar
  • 51
5 votes
2 answers
492 views

Clarification on the TLS verification process

I am reading this article in my attempt to understand how the TLS verification and chain of trust works. In the piece I come across a section that I am not sure I understand. In the simplified ...
user avatar
5 votes
2 answers
283 views

Can S/MIME be still considered secure?

Previoulsy I had asked this question at https://stackoverflow.com/questions/18235983/can-s-mime-be-still-considered-secure but I feel this forum is topic-wise the right place. Recently there has been ...
user avatar
5 votes
4 answers
20k views

Diffie-Hellman and man-in-the-middle attacks

See here for the man-in-the-middle attack on Diffie-Hellman that I'm concerned about: What is Diffie-Hellman? How do we combat this? I have two questions: Is one solution for both Alice and Bob just ...
user avatar
  • 307
5 votes
4 answers
10k views

Diffie-Hellman Key Exchange with Authentication: Man-in-the-Middle query

I have been reading up on MiTM attacks, and the prevention of them using public key certificates. Recently I learnt about Diffie-Hellman Key Exchange with Authentication, and how it uses signed ...
user avatar
5 votes
2 answers
1k views

What is cryptographic sealing?

While revising my CAdES library I encountered some "sealing issue" in digital signatures. The Win SDK signtool.exe has a /seal ...
user avatar
5 votes
3 answers
12k views

Is there a complete list of Signature Algorithm names?

I need to analyze the output of rbsec's sslscan which reports a server's SSL/TLS configuration as reported by OpenSSL. I'm interested in the Certificate's Signature Algorithm in particular, and I was ...
user avatar
5 votes
2 answers
900 views

Smart Card - Entropy during on-board public key generation

I know that some (advanced) smart cards or tokens allow generating key pair directly on the device, but I wonder how the card can gather entropy during the process. Any idea ?
user avatar
5 votes
1 answer
139 views

Signature verifying against multiple certified public keys?

I'm wondering if and how the current public key certificate infrastructure is guarded against the following scenario: Honest Alice obtains Eve's public key certificate Certe, made by honest CA Carol; ...
user avatar
  • 122k
4 votes
2 answers
1k views

Why is the signatureAlgorithm field in X.509 certificates redundant?

See the ASN.1 description of an X.509 certificate below: ...
user avatar
  • 785
4 votes
2 answers
4k views

Certificate Authority RSA key expiration?

My understanding about SSL/TLS for HTTPS is that servers send their certificates to browsers and browser attempt to decrypt them using trusted CA public keys that are already presented in their store. ...
user avatar
  • 175
4 votes
1 answer
6k views

Trying to understand the use of ECC in TLS certificates

I was looking the certificate of this website: https://www.cloudflare.com that has an ECC based certification. I'm just curious to know if is possible to understand which elliptic curve is used and ...
user avatar
  • 103
4 votes
4 answers
3k views

Signature and Timestamp for Long Term Document Archival Question

I have a PDF document intended for long-term (many years, maybe decades) archival which I would like to digitally sign with my personal certificate to ensure its integrity. As far as I understand, I ...
user avatar
  • 141
4 votes
2 answers
9k views

Why does curl need both root and intermediate certificates in order to securely connect to an HTTP server?

I have created a root certificate, an intermediate certificate, and a server certificate: ...
user avatar
  • 197
4 votes
1 answer
1k views

What is the maximum length of a X.509 OID?

I'm working on a feature for a project to determine if a given X.509 certificate is an EV Certificate, and if so, who is the authority behind that certificate. To do this, I grabbed the list of EV ...
user avatar
  • 143
4 votes
1 answer
1k views

What information is signed by a Certification Authority?

What data does a CA sign? I know that in a certificate there is plenty of information such a the serial number of the certificate itself, the X.509 version number, the user public key, the asymmetric ...
user avatar
  • 1,158
4 votes
2 answers
4k views

What exactly is Let's encrypts chain.pem file?

While trying to understand the use or meaning of the fullchain.pem file created by let's encrypt I stumbled upon this post in which ...
user avatar
4 votes
1 answer
2k views

OpenPGP/X.509 bridge: how to verify public key?

I'd like to use OpenPGP authentication over TLS, but lack of implementations made me use a temporary solution: an OpenPGP/X.509 bridge certificate. The approach is very similar to the approach used in ...
user avatar
4 votes
1 answer
2k views

How does certificate-based encryption solve key revocation problem?

How does certificate-based encryption solve key revocation problem? For example, if a user accidentally reveals its secret key or an attacker compromises it, the user may request revocation of its ...
user avatar
  • 67
4 votes
2 answers
2k views

How is SSL secure from rogue Certificate Authorities?

There's one thing that I've never quite understood about SSL (which perhaps means I don't understand SSL at all): how is SSL secure from rogue Certificate Authorities? This is probably best ...
user avatar
4 votes
2 answers
7k views

How do digital certificates work, and why is it not possible to reverse engineer one from a signed file?

Digital certificates are used quite commonly these days, for signing files. They are used by various operating systems to ensure reliability and security. For example, Android requires that each of ...
user avatar
4 votes
1 answer
94 views

Why are some websites seemingly immune to self-signed certificate MitM attacks?

I recently did an experiment using MitM to gain account information (username and password) while accessing websites. I used two PCs in the scenario; one as the target, running Internet Explorer, and ...
user avatar
  • 143
4 votes
1 answer
184 views

How is the root certificate transmitted to pc?

i understand that the purpose of root certificates and CA's is to ensure that the communication parties are who they say they are. But how is the root certificate acquired? Is it not possible that ...
user avatar
  • 199
4 votes
1 answer
159 views

What security do digital signatures provide (like used when signing PDFs)?

I want to ask you one question about digital signatures as they are (for example) used when digitally signing PDFs. We know that if our document has a digital signature, we can detect if the original ...
user avatar
  • 41
4 votes
1 answer
6k views

x509 Certificate Signature

I've got a question about the signature of a CA. As I understand, the CA takes the public key of the client and signs it with his own private key by using "md5WithRSAEncryption" (like explained here: ...
user avatar
4 votes
0 answers
705 views

RSASSA-PSS in TLS 1.2

I know it is possible to use RSASSA-PKCS1-v1_5 with client certificates in TLS 1.3. But what about the other way around: using RSASSA-PSS with client certificates in TLS 1.2? Is it possible to use ...
user avatar
  • 41

1
2 3 4 5 6