Why You Should Never Store Passwords in Plain Text: A Practical Guide to Hashing and Salting

In the era of cyber‑attacks, storing a password exactly as the user types it is an open invitation to criminals. An irreversible hash and a unique salt per account are the pillars that prevent a compromised database from becoming a list of usable credentials. In this article you will discover, step by step, what hash functions are, how Rainbow Table attacks work, and why salting is indispensable for protecting your users.

1. Hash functions: the foundation of password security

A hash function is an algorithm that transforms any string (for example, a password) into a fixed‑length, irreversible string. As the Pockit Tools article notes, hash functions are one‑way, meaning there is no practical method to go from the hash back to the original password.

When a user creates or updates their password, the system:

1. Takes the plain‑text password.
2. Applies the hash function (e.g., SHA‑256, bcrypt, or Argon2).
3. Stores only the hash in the database.

Thus, even if an attacker manages to steal the user table, they will obtain only hash values that cannot be directly reversed. As ITD points out, “a password never needs to be read again, not even by you, so an irreversible ‘hash’ is the correct answer.”

2. The danger of Rainbow Table attacks

Although hashes are one‑way, techniques exist that try to speed up the search for the original password. Rainbow Tables are pre‑computed databases that map common hashes to their possible passwords. If an attacker has a table covering the algorithm used, they can quickly compare stolen hashes and discover the original password.

This risk becomes critical when simple, unsalted hashes are used. The Fundación de Valores explains that the password‑verification mechanism without storing readable text relies on the hash being unique; otherwise, identical hashes for identical passwords make the attacker’s job easier. Hence, a hash alone is not enough.

3. Salting: the trick that breaks uniformity

Salting consists of adding a random value (the “salt”) to the password before applying the hash function. Each user receives their own salt, which is stored alongside the hash. As Plisio describes, “the salt is the random value that is mixed with the password right before hashing; it’s the trick that makes every stored hash unique, even for shared passwords.”

Key advantages of salting:

• Unique hash per user: Two users with the same password will have different hashes, preventing a Rainbow Table from being useful for both.
• Protection against massive brute‑force attacks: The attacker must recompute the hash for every password‑salt combination, exponentially increasing the required time.
• Ease of implementation: Most modern algorithms (bcrypt, scrypt, Argon2) incorporate the salt automatically, as ITD emphasizes when mentioning “combine a per‑user salt with a slow hash (bcrypt/Argon2).”

4. Slow hash algorithms: bcrypt, scrypt, and Argon2

Not all hash algorithms are suitable for passwords. Fast hashes (like SHA‑256) are designed for speed, making them vulnerable to brute‑force attacks. In contrast, bcrypt, scrypt, and Argon2 are “slow” algorithms that deliberately consume more CPU and memory resources.

• bcrypt: Introduced in 1999, it includes a configurable cost factor that determines how many iterations are performed.
• scrypt: Adds intensive memory usage, making GPU parallelization difficult.
• Argon2: A modern algorithm designed specifically for password hashing, with variants that prioritize memory (Argon2i) or performance (Argon2d).

Programming YA tutorials stress that “for passwords you should use dedicated key‑derivation algorithms like bcrypt, scrypt, or Argon2.” These functions, combined with a unique salt, ensure that even if an attacker obtains the hash table, breaking each entry will be costly and unprofitable.

5. Best practices for implementing hash and salt

1. Choose a modern algorithm: Prefer Argon2 or bcrypt based on what’s available in your stack.
2. Generate a random salt per user: Use a cryptographically secure generator (e.g., os.urandom in Python).
3. Store only the hash and the salt: Never keep the password in plain text or in a reversible form.
4. Increase the cost over time: As hardware improves, raise the cost factor or memory parameters to maintain resistance.
5. Perform verification tests: When authenticating, combine the entered password with the stored salt and compare the resulting hash to the stored one.

Escuela de Programación provides concrete examples in several languages (Python, PHP, Node.js, and Java) that illustrate how to correctly apply these steps.

Conclusion

Storing passwords in plain text is a vulnerability that any organization should eliminate immediately. One‑way hash functions, Rainbow Table attacks, and the need for a unique salt are essential concepts for building a robust authentication system. Adopting slow hash algorithms like bcrypt or Argon2, and following the best practices outlined above, guarantees that even if a database is compromised, attackers cannot turn the hashes into usable passwords.

Ready to strengthen your users’ security? Review your application code, replace any plain‑text storage with a hash + salt process, and keep cost parameters up to date. Security is not an option; it’s a continuous responsibility. Start today and protect your users’ trust!

Sources and references

• Por qué nunca debes almacenar contraseñas en texto plano ...
• Cómo guardar contraseñas: hash y salt (Argon2/bcrypt) | ITD
• ¿Qué es el salting en seguridad? Hash de contraseñas en 2026
• Hashes — Cómo Guardar Contraseñas de Forma Segura
• Qué es el hashing y cómo proteger contraseñas en tu aplicación

Divulgación (normas IA de DEV): este artículo fue elaborado con asistencia de IA — Jarvis, un asistente autónomo corriendo en una Raspberry Pi —, verificado contra las fuentes citadas y supervisado por Sergio antes de publicar.