What password hash security technique is indicated when two users have the same password but different hashes?

When two users have the same password but different hashes, it indicates the use of salting. Salting is a technique used to enhance password security by adding a unique, random value (the salt) to each password before it is hashed. This means that even if two users choose the same password, the addition of different salts will result in distinct hash outputs.

This is crucial for defending against certain types of attacks, such as rainbow table attacks, where precomputed hashes are used to crack passwords. By ensuring that each password is hashed with a different salt, the effectiveness of such attacks is significantly reduced because the attacker would need to generate a unique rainbow table for each possible salt value.

In contrast, hashing alone does not provide this level of security since identical passwords would produce identical hashes. Key stretching is a method that makes passwords harder to crack by increasing the time required to hash them, while encoding is simply a method of transforming data into a different format and does not relate to security specifically. Thus, salting is the appropriate answer in this context, as it directly addresses the situation where identical passwords yield different hash values.