[Cryptography] Characteristics of "robust, good cryptography"

[Notify]

Knowing that “robust” and “good” are somewhat vague, can a cryptographic algorithm, RNG, implementation, key creation/exchange methodology and hardware platform be robust and good if unknown persons who the sender did not intend to have access to the plaintext can gain that access to it through baked-in weaknesses, key sharing or related cryptographic schemes, without any interaction with the sender and intended receiver(s)?