I was wondering whether RSA can be cracked given:
The public key
A plaintext of a known cipher text.
In other words the decrypted message from an encrypted one (but without knowing the private key)
I.E.: you have managed to find the plaintext of an already encrypted message using the public key, however, you DO NOT know the private key.
No. That's called a known-plaintext attack, and there is no such attack known against RSA.
Related
I have private key (not RSA) and i want to generate JWT using <jwt.io> using RS256. How can I generate a token?
Whenever I enter my private key it says invalid signature. If I need to pass RSA private key then how to convert my private key to RSA private key? I am totally new to this.
RS256 is an asymmetric signature algorithm, that means you need a keypair consisting of private and public key. You can generate such a pair with various online tools or with openssl.
To generate (i.e sign) a token, you need the private key.
But for verification, you need the public key. As long as you only paste the private key into the field in the right column, JWT.io can sign a token, but can't verify it. Therefore paste both keys of the pair into the key fields to get your token signed and verified.
I am new to Swift Language . I wanted a swift code for decrypting a message using RSA Public key.
Padding used is "PKCS1". (I am not talking about Signature , I want the code for decryption of message itself using Public Key) .
Thanks in Advance
I wanted a swift code for decrypting a message using RSA Public key.
What you are asking for is not possible.
With RSA public keys are used to encrypt messages, while the private key is used to decrypt encrypted messages. It's the other way around with signatures, and probably the reason why you are confused. Signatures are created using the private key and can be verified by public keys.
I need to write a method in Swift which uses a particular PRIVATE KEY to encrypt a timestamp using RSA. This is NOT used for authentication (rather it validates the client app to the server), I know that you would normally encrypt with a public key to ensure security.
I have a key:
-----BEGIN RSA PRIVATE KEY-----
MIICXAIBAAKBgQDIg+wteSjhalc1hSHEiUnz9X1pkrObCjaXMHqeSdfFQ/h5Q1Uh
...
o7wjoqFNxFnQMAYvkLzQZ7Y2jjfSJkaTVnhzJIZOfQ0=
-----END RSA PRIVATE KEY-----
And I need to encrypt a string using this particular key. I have written the Android application version of this app, but if I need to re-generate the keys specifically for iOS it's not a problem, but I would need this file for the Android version as well.
I have looked at the following web sites:
http://jslim.net/blog/2013/01/05/rsa-encryption-in-ios-and-decrypt-it-using-php/ Seems useful but it insists that the key be in a .der format - plus it's in Objective-C. Is it possible to generate a Key pair in both DER and PEM format, or convert between the two (using something like https://www.sslshopper.com/ssl-converter.html)?
https://github.com/henrinormak/Heimdall - but you cannot import a custom private key
https://github.com/ideawu/Objective-C-RSA/blob/master/RSA.m - seems long winded and is also in objective-c
One requirement is that all apps use the SAME key - it cannot be generated by each installation of the app. Also my Android app must be able to use the key as well (I am open to rethinking the Android version as leaving the key as a RAW file is not preferred for me).
Any help will be appreciated.
Other references checked:
How to encrypt a string with private key and decrypt with public key?
Using RSA public key to encrypt a string
Can anyone help with the code how to decrypt with private key ,As in server side they are using OAEP encryption method .I tried decrypting using private key but the decrypted text is Null,I am getting the Error code as -9809 as decryption code result
When you say "with a private key" I assume you mean you're using SecKeyDecrypt() for asymmetric encryption rather than CommonCryptor for symmetric encryption.
SecKeyDecrypt() does not support OAEP. It only supports PKCS1 v1.5 padding (kSecPaddingPKCS1). It can also technically handle ASN.1 padding + PKCS1 padding, but this isn't usually relevant to decryption. You should have noticed this when you passed the SecPadding parameter. What did you pass?
That error number is errSSLCrypto which is a generic "something went wrong in crypto" message.
I am reading about application code signing in iOS and I don't understand why both private and public key is together? What is the public key and certificate used for when you are signing the application with the private?
Xcode uses your digital identity to sign your application during the
build process. This digital identity consists of a public-private key
pair and a certificate. The private key is used by cryptographic
functions to generate the signature. The certificate is issued by
Apple; it contains the public key and identifies you as the owner of
the key pair.
Let's sum up the process:
You encrypt an hashed digest (like md5 or sha-1) of the executable of application with your private key. That's "signing".
Your users decrypt it with your public key (they have it because it's public) and check it against the executable. As long as your private key stays private, it's you who "signed" it. That's called "verifying".
What about the digital identity then:
You public key isn't public by itself, it must be somehow shared, "made public", and signed by the Certification Autority (hereby CA) too, (that's the CA encrypting it —or an hash of it— with their, one of their, magical mysterious private keys) this guarantees the sharing process hasn't been tampered with by a man in the middle.
So, public key and certificate (CA signature — CA encrypting your public key) identify you (as such are considered part of your "digital identity") and must reach the end user somehow (via a third party, embedded into the executable, you name the way)
The public key is needed so anyone can decrypt the application, and is hence included in the build.