Cracked

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

Cracked

#Edit I made a mistake. New code which is more secure to the obvious attack:

main(a,_){puts(_*_-1||_*_*_-1||_*_*_*_-1?"Expected Output":"?");}

same outputs. New size of 65 bytes. Hopefully harder... though still probably too easy.

Cracked

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

Cracked

#Edit I made a mistake. New code which is more secure to the obvious attack:

main(a,_){puts(_*_-1||_*_*_-1||_*_*_*_-1?"Expected Output":"?");}

same outputs. New size of 65 bytes. Hopefully harder... though still probably too easy.

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

#Edit I made a mistake. New code which is more secure to the obvious attack:

main(a,_){puts(_*_-1||_*_*_-1||_*_*_*_-1?"Expected Output":"?");}

same outputs. New size of 65 bytes. Hopefully harder... though still probably too easy.

Cracked

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

Cracked

#Edit I made a mistake. New code which is more secure to the obvious attack:

main(a,_){puts(_*_-1||_*_*_-1||_*_*_*_-1?"Expected Output":"?");}

same outputs. New size of 65 bytes. Hopefully harder... though still probably too easy.

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

#C, 53 bytes

##Code

main(a,_){puts(_*_*_*_*_-1?"Expected Output":"?");}

##Original Output

Expected Output

##Changed output

?

Probably too easy, but who knows. (Note: it is technically system dependent but the type of system on which it fails would also fail all the other submissions here, so I figured it was a moot point).

#Edit I made a mistake. New code which is more secure to the obvious attack:

main(a,_){puts(_*_-1||_*_*_-1||_*_*_*_-1?"Expected Output":"?");}

same outputs. New size of 65 bytes. Hopefully harder... though still probably too easy.