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How do RSA keys work?
An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value. The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers. Breaking RSA encryption is known as the RSA problem.
What makes RSA secure?
RSA security relies on the computational difficulty of factoring large integers. As computing power increases and more efficient factoring algorithms are discovered, the ability to factor larger and larger numbers also increases.
Is it safe to use the same RSA keypair?
The RSA signature operation is basically the same as encrypting with the private key. In particular, both operations use the same kind of keys. Is it safe to use the same RSA keypair both for encryption / decryption and for signing / verification?
Can We have multiple public keys with a single private key?
However given one of the usual asymmetric schemes you can easily create such a scheme: To create a private key with n public keys, just generate n public-private keypairs in the normal scheme and define the “private key” to be the collection of the private keys.
Is it safe to use raw RSA for encryption?
However, the raw RSA operation has a whole range of other flaws that make it unsafe as an encryption or signature scheme. Encryption and signature schemes based on RSA use padding modes. The standard padding modes include discriminants so that an encryption payload does not look like a signature payload.
Is the output of RSA always less than the modulus?
The output of the RSA encryption is of course always less than the modulus. As part of the PKCS#1 algorithm it is put through the I2OSP transformation (see the RFC). This encodes the resulting number from the calculation to an octet string (or byte array) with the same size as the modulus, in bytes.