The standard criterion for security is indistinguishability under adaptive chosen-ciphertext attack, or IND-CCA2. What this means is that the adversary is given:
the public key $(n, e_B)$, and
an oracle that answers queries of the form: What is the plaintext for the ciphertext message $c$?
The adversary's task is to find any pair of messages with a ...
Why is this not a problem?
Because for two different encryptions the random integers are drawn independently and uniformly at random over the whole range of the multipicative group $\mathbb Z_N^*$ (in practice this is usually approximated as $[1,n)$). The RSA assumption now literally states that it's difficult to recover the random value from its textbook ...
What is the difference between PKCS#1 v1.5 and PKCS#7?
PKCS#7 makes use of cryptographic primitives defined by PKCS#1 v1.5.
PKCS#7 is defined in RFC 2315. The modern PKCS#1 is v2.2 (also RFC 8017), and has a modern description of the schemes in PKCS#1 v1.5, including RSASSA-PKCS1-v1_5.
Is verifying a PKCS#1 v1.5 signature the same as verifying ...