Template:User committed identity/doc

This template gives you a way to later prove that you are the person who was in control of your account on the day this template was placed. This is done by putting a code (called a "hash") on your user page so that, in the event that your account is compromised, you can convince someone else that you are really the person behind your username.

Why?

The intended use of this template is to help in the hopefully unlikely event that your account is compromised. If you published your real-life identity, then that identity could be used to reestablish contact with you if your account were compromised; keep in mind, in this scenario contact could not be established with you through your account, since it may be under the control of someone else. However, many Wikipedia users do not disclose their real-life identities, or disclose little enough of them that it may be difficult to establish their identity.

This is not a replacement for having a strong password, nor for registering an email address for your account. You should still do everything you can to prevent your account being compromised, including using a strong password and remembering to log yourself out when using a computer others may have access to. If you have one, it may also be helpful to post your PGP public key. But even with the best of precautions, your account could become compromised, for instance, via a trojan horse or a brute-force attack on your password. This is intended to be a last resort.

How

The idea is to use cryptographic hashes; you choose a secret string known only to yourself, put it through a one-way hash function, and publish the result somewhere. It is infeasible to determine the secret string corresponding to the hash; hence, an attacker compromising an account presumably would not be able to supply the secret string.

Syntax

{{user committed identity|hash|hash function used|background=CSS color|border=CSS color|article=grammatical article for the hash function}}

Italicized text should be replaced with appropriate input, or its parameter should be removed. Parameters are represented by 'parameter=value", and separated by vertical bars |.

• Replace "hash" with the hash produced from your secret string. The implicit name of this parameter is "1" (see numeric parameters).
• The "hash function used" parameter, if not included, defaults to SHA-512. (This hash function is strongly recommended.)
• The "background" parameter, if not included, defaults to #E0E8FF (light blue, see Web colors#Hex triplet)
• The "border" parameter, if not included, also defaults to #E0E8FF.
• The "article" parameter, if not included, defaults to "a". The other likely value is "an".

For example, if your hash is "ef7c4c55a176bd20ed558aaefde21c4803080195" using SHA-1, and you want a light orange box with a black border, use the following code

{{user committed identity|ef7c4c55a176bd20ed558aaefde21c4803080195|SHA-1|background=#FC9|border=#000}}

to produce

Committed identity: ef7c4c55a176bd20ed558aaefde21c4803080195 is a SHA-1 commitment to this user's real-life identity.

Choosing a good secret string

1. Your secret string should not be easy to guess. If your string is easy to guess, then the fact that you know the string is not likely to be very persuasive. For example, a string of 'joe' will be less convincing than 'My name is Joe Schmoe, and I can be contacted at: joe@example.com'
2. Your secret string should specify enough of your identity that, if the string were revealed, you could unambiguously prove you match that identity. For instance, your secret string could include a telephone number or email address at which you can be reached.
3. Try not to choose a secret string that represents your identity that could go completely out of date. So, for instance, it may be bad to choose a string that specifies only your telephone number as that number might change.
4. If you want to change your secret string, do so, but keep track of all your old secret strings. It is best to reveal all of them if you ever want to confirm your identity, as this will establish that you are the same person who used your account from the first moment the committed identity was published.
5. Your secret string should not be short. A dedicated attacker could, by brute force, try short strings until they find your secret string, but if your string is longer that attack would be impractical. If your string is 15 characters long, there are around 10²⁷ strings of that length, or an octillion (and that's just counting alphanumeric strings with spaces).
6. Your secret string should not only contain an email address, name, or phone number, but should contain hard to guess components. "jsmith@hotmail.com" for example may be vulnerable to both dictionary attacks and a search of email addresses, enabling attackers to check 'only' those hundred million names against all published hashed identities, which is computationally much easier than trying to identify a randomly chosen string.

Getting the hash

Be sure to note the exact string you enter into the form, in case you need to use it later. It is important that this string be both easily remembered exactly by you and hard to guess or find by any intruder - if an intruder knows the secret string, then this scheme is useless and provides no security. One's username is public and trivially guessable; one's password is not a good choice either, as in the event of a compromised account, the password is likely to have been guessed.

On Unix-like operating systems the md5sum, sha1sum, sha224sum, sha256sum, sha384sum, and sha512sum programs are provided in the GNU Core Utilities. Windows users may use one of the methods mentioned below; those who have PowerShell installed can generate a hash using the following command. Provide your secret phrase in the location indicated:

[bitconverter]::tostring((new-object security.cryptography.sha512managed).computehash([text.encoding]::utf8.getbytes("Secret phrase here"))).replace("-", "")

It is recommended that SHA-512 be used, as recent cryptographic research has cast doubt on the long-term security of SHA-1. The template defaults to SHA-512 if the hash function parameter is omitted. For security, you should only use locally executed programs, or client-side javascript, to create your hash. Examples of such hash calculators include jsSHA and HashCalc 2.01.

To verify that you are correctly hashing your secret string, you can try hashing 'My name is Joe Schmoe, and I can be contacted at: joe@example.com' (without the enclosing single-quotes). Your SHA-512 hash should be: b7a84efbbd843545666957384e874c894fdc17f48ced53abd231c2e4d08e45ad10287b1225432e3ed9794c12994ff1e82aecf66a2ded61ad4baf6d8b9c81dab8

Compromised identities

In case your account is compromised, to make use of your committed identity to someone and prove you are the same person who originally controlled the account, give a trusted user the exact secret string you originally entered into the box. They can then compute the appropriate hash of that same string and verify that it is the same result and that you are who you say you are.

Once you've established your identity, and set up a new account or regained control of the original account, you'll probably want to create a new hash as now someone (possibly multiple someones depending on who and how you told the secret string to) else knows the secret string.

Weakness

This technique of establishing identity by revealing the secret string behind the hash is not inherently attack proof; it increases attacker effort substantially (if the secret string is chosen and handled properly) which is worthwhile, and does so at little effort to the legitimate user. But it is attackable in that anyone can invent their own secret string, hash it, and claim an identity.

An attacker with access to the account could overwrite the hash with their own one. They could then say that the previous owner of the account was an attacker who claimed their identity and generated his own hash.

An attacker without access to the account could claim that the current account's owner stole their identity. The attacker could state that they did not publish a hash when they used to own the account, or that they did not register an account and that someone else is using their name.

This weakness does not indicate the commitment scheme is worthless, because the commit phase did not apply to all interested parties (the real person and all potential attackers).

See also

• Don't leave your fly open (essay)
• Strong password
• Wikibooks:Requests for renaming