The below leads to a series of interrelated questions.
It is generally accepted that encrypted data is almost impossible to decipher without the correct key. Examples given are like finding a grain of sand on a beach in the solar system. Pretty awesome!
You wrote above, 'Encryption transforms human readable plaintext into something unreadable, also known as ciphertext'.
Would the data that is exchanged as a ciphertext using a known cryptographic program produce predictable patterns of data/ciphertext?
If the same identical plaintext was produced, transmitted or recorded twice using the same cryptographic program, would the resulting ciphertext also be identical?
If the ciphertext was identical, why would one not be able to break the cryptographic program by making small changes to the original data and then identifying these changes in the resulting ciphertext?
For example, if one changed one letter after another in a persons name and then noted the difference in the resulting ciphertext, could one not extrapolate the workings of the ciphertext? Thank you.