Scenario
A SOAP web service provides an interface for retrieving documents and data. Security is paramount.
WS-Security is used and both the client and server encrypt and sign the entire SOAP envelope.
Questions
Should the private key used for signing be compiled into the application and stored on the device or should it provided by the server using a key exchange protocol (perhaps after authentication of the user)?
Should the private key for decryption be stored on the device or provided by the server?
Is it realistic to have a unique key for each file that is to be decrypted by the server (if uploading from client) or decrypted by the client (if downloading from server)?
Just a couple suggestions:
-You should consider symmetric keys embedded into anything outside your server as public due to reverse engineering (i.e. don't bother even encrypting if the key is out in the wild).
-You should use a per-session symmetric key generated by a secure RNG on the client, and transmitted to the server encrypted with the global asymmetric public key. Private keys have a shelf-life.
-You can use the session key for all files/streams transferred in that session, but you should use a unique nonce to salt the symmetric-key encryption for each file. Depending on the encryption mode, using the same key/nonce with more than one stream can leave you vulnerable to XOR'ing the two streams and recovering a mashed-together but unencrypted result.
The entire concept of a private key is defeated if it has to be transmitted from one device to another. Each end of the communication channel must generate their own private keys. Note, that this doesn't mean compiling private keys into an executable, because then everyone with the executable shares a private key, which is obviously not what you want. Each individual device has to use a cryptographically secure source of random numbers to generate it's own public/private key pair. Then public keys can be exchanged in the clear, you can use them to exchange session keys (which can be unique for each and every file), private keys can sign, and everybody is happy.
But remember: Never, ever hard code private keys, and never, ever share them with anybody.
Related
So, I'm building an application for MTLS authentication and generate X509 certificates using AWS ACM PCA and bundle them together with a private key in PKCS#12 format.
At the moment I generate key pairs programatically in Java which are never stored.
But since I'm not a security expert I thought maybe it's better to use AWS KMS for creating key pairs.
So, it seem like what I need is a CMK which can generate data key pairs which are stored in KMS.
If they're stored in KMS and I can fetch the private key at any time, how is that more secure than not storing it at all?
Or is the purpose of KMS only to store keys securely?
If you have a use for the encrypted private key that kms.generateDataKeyPair will provide, then it would be of use. It would also be a nice way to ensure that your keys are being generated securely (secure randomness, etc).
It’s important to note, KMS will not store the generated key pair. The idea is that you would store the plaintext public key, and the encrypted private key, and call kms.decrypt to turn the encrypted private key into plaintext whenever you need it.
At the moment I want to implement a method that stores certain data server-side only encrypted. For this procedure is provided that each authorized user receives a private key, with which he can store and read encrypted data. Now it is so that several authorized persons are allowed to look at the same encrypted content. This means that if person A stores data encrypted with his private key, person B (if authorized) can also read this data with his private key.
The idea of implementation:
For all authorized persons, a single symmetric key is generated on the server side. The key is used to encrypt and decrypt plain text data. Now, for each individual claimant, a key pair is generated (public and private). With the public key, the symmetric key is encrypted and stored for the user and there are several of these asymmetrically encrypted symmetric keys on the server. The private key is given to the user (as a file download, HTTPS), which later can be used to decrypt the encrypted symmetric key. Therefore He can upload his private key before writing or reading encrypted data, in a web application (client side) and send it to the server. The Server uses the private Key to encrypt the content of the user and save it, or decrypt older content and send it in plain text to the user.
My problem now is that the weak point is the server, where the private key of the user must first be sent to encrypt and decrypt. There might be someone with access this private key secretly intercept and save.
My question now: Is there an alternative to the approach or does one have to do so if he wants to implement such a procedure? It is important that the data is stored only encrypted. And also this must be implemented with a client web-application and a backend.
i want to know performance wise which is better to provide message authenticity, ECDSA signatures or hash based signatures, although i have read the comparisons of ECDSA with RSA, but not found with hash based signatures. Can ECDSA signatures replaced with Hash based signatures improves the message authenticity or not.
ECDSA is a hash based signature, in that the data gets hashed, then ECDSA is performed on the hash (not the whole data)
When it comes to data verification there are three main approaches:
Straight hash (e.g. SHA-2-256)
The fastest option to verify
If you are only protecting against line corruption this is a valid choice.
Otherwise, requires that the hash/digest value be sent over a secure (from tamper) channel, because the tampered can easily transmit the digest along with the tampered document
Provides no proof of origin
HMAC (e.g. HMACSHA256)
Requires that both the sender and receiver share the secret key
Either the sender or receiver having the key stolen puts both sides at risk
Secret key needs to come from key agreement algorithms (ECDH) or be transmitted in secret (encrypted)
Proves the document came from someone with the shared secret.
Digital Signature (e.g. ECDSA, RSA signature)
The sender is the only entity with the private key, receiver needs public key (non-secret)
Public key can be embedded in an X.509 certificate to provide a notarized association of public key to the signer
Or the public key can be transmitted raw over a secure (from tamper) channel.
Provides strong assurances about the document origin, since they shouldn't share their private key.
All three options use a hash algorithm to reduce the original data, the rest of the algorithms are what do you do with that data. There's not really a standard definition of "secure", you have to say "secure against (something)". ECDSA provides more assurances than HMAC as long as the private key isn't shared. But if HMAC provides enough assurance it is probably faster on average (specialty hardware aside).
In case of claim based authentication which uses SSO, an application receives a token from the issuer for a particular user and that token contains the claims as well as some sort of digital signature in order to be traced by the application that an issuer is a trusted one.
I want to know, if there are some sort of algorithms involved by which this application recognizes an issuer?
I had read that issuer has a public key and all the other applications have their own private key, is it true?
There are many protocols, formats and methods of doing Single Sign On such as Security Assertion Markup Language (SAML), OpenID and OAuth. The goal is for one entity, such as a website, to identity and authenticate the user (such as through a user name and password) and other entities, such as other websties, trust the evidence of that authentication through a token. This means users need not remember yet another password and each website maintain their own list of passwords.
This trust is usually enforced through cryptography using a digital signature. Digital signatures are used because it allows the trusting entity to verify token was (1) issued by the authenticating entity only and (2) not tampered with without being able to impersonate (pretend to be) the authenticating entity.
As you say above, this is performed using asymmetric or public key cryptography. Symmetric cryptography, such as the AES or DES algorithms, use a single key to encrypt and decrypt data. Asymmetric cryptography, such as the RSA algorithm, uses two related keys. Data encrypted using one can only be decrypted by the other and vice versa.
One key is usually kept secret, called the private key, and the other is distributed widely, called the public key. In the example above, the authenticating entity has the private key that allows it to encrypt data that anyone with the public key can decrypt.
It would seem to follow that the authenticating entity would just encrypt the user details and use that as the token. However, commonly used asymmetric algorithms like RSA are very slow and encrypting even small amounts of data can take too long.
Therefore, instead of encrypting the user details, the authenticating entity generates a "hash" or "digest" and encrypts that. A hash algorithm converts a piece of data into a small number (the hash) in a very difficult to reverse way. Difference pieces of data also create different hashes. Common hash algorithms include Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) and its derivatives like SHA1, SHA256 and SHA512.
The hash encrypted with the authenticating entity's private key is called a digital signature. When it receives the token, the trusting entity decrypts the token using the authenticating entity's public key and compares it to a hash it calculates itself. If the hashes are the same, the trusting entity knows it has not been modified (because the hashes match) and it must have come from the authenticating entity (because only it knows its private key).
If you want more information about SAML and claims-based authentication, I found this video very helpful. It does get complicated rather quickly and you may need to watch it multiple times but Vittorio covers most of these concepts in great detail.
I'm working on a Single Sign On solution to allow my company to integrate with other vendors.
As I'm doing my research, one thing is constantly confusing me.
My understanding of Public/Private key is that data is always encrypted with the vendor's public key and they decrypt using their private key. So far so good.
However, to validate that the message is really coming from me, I will compute the hash of the message and encrypt the hash with my private key (this process is also known as signing). To verify that the message is coming from me, the vendor will use my public key to decrypt the Hash and compare it with the unencrypted hash. If they match, the vendor can be confident that it came from me.
So how come my private key is used to encrypt the message..and how can public key decrypt the message? I thought Asymmetric keys doesn't allow that..! i.e Public Key always encrypts and private key always decrypts. Any explanations will be greatly appreciated..!
Encryption and signature are two different systems. In some ways, they work in opposite directions.
With public-key encryption, anybody can encrypt data with the public key. Only the owner of the private key can decrypt encrypted messages to recover the data.
With signatures, only the owner of the private key can sign messages. Anybody can use the public key to verify the signature of a message.
My understanding of Public/Private key is that data is always encrypted with the vendor's public key and they decrypt using their private key.
That's correct. But it only covers public-key encryption, not other uses of public-key cryptography such as signatures.
However, to validate that the message is really coming from me, I will compute the hash of the message and encrypt the hash with my private key (this process is also known as signing).
Actually, this process should only be known as signing. Calling it “encrypting with my private key” is very misleading: that's not the way it actually works. There is one popular type of keys (RSA) which can be used for both signature and encryption, but even with RSA, the signature and decryption mechanisms are different.
To verify that the message is coming from me, the vendor will use my public key to decrypt the Hash and compare it with the unencrypted hash. If they match, the vendor can be confident that it came from me.
That's not quite correct. Many signature algorithms are not deterministic. Verifying a signature is not done by reversing the signature process, but by making some slightly different calculations involving the signature, the message and the key.
So how come my private key is used to encrypt the message..and how can public key decrypt the message? I thought Asymmetric keys doesn't allow that..! i.e Public Key always encrypts and private key always decrypts. Any explanations will be greatly appreciated..!
The private key is used to sign the message, not to encrypt it. The public key is used to verify the signed message, not to decrypt it.
i found this link very helpful :
http://www.nusphere.com/products/library/ssl.htm
Wayback Machine archive from 2007 of the above nusphere link.
HTH
Ohad
EDIT
after 2.5 years, I see that the link is broken. So this one is good as well.
And in case it will be broken again in 2.5 years from today, here is the summary:
The Public Key is what its name suggests - Public. It is made
available to everyone via a publicly accessible repository or
directory. On the other hand, the Private Key must remain confidential
to its respective owner.
Because the key pair is mathematically related, whatever is encrypted
with a Public Key may only be decrypted by its corresponding Private
Key and vice versa.
Public Key Cryptography can therefore achieve Confidentiality. However
another important aspect of Public Key Cryptography is its ability to
create a Digital Signature.
The difference between symmetric and asymmetric encryption is only the existence of private and public keys.
Nevertheless in the common algorithms you can use the private key to encrypt messages which can be decrypted with the public key and you can also decrypt messages which are encrypted with the public key. So it is possible in both directions.