Confidentiality has been defined by the International Organization for Standardization (ISO) as "ensuring that information is accessible only to those authorized to have access" and is one of the cornerstones of Information security. Confidentiality is one of the design goals for many cryptosystems, made possible in practice by the techniques of modern cryptography.
Confidentiality also refers to an ethical principle associated with several professions (eg, medicine, law, religion, journalism,…). In ethics, and (in some places) in law, some types of communication between a person and one of these professionals are "privileged" and may not be discussed or divulged to third parties. In those jurisdictions in which the law makes provision for such confidentiality, there are usually penalties for its violation.
Journalists often recognize several levels of confidentiality with news sources. They are:
- On the record — Information provided "on the record" may be quoted and attributed directly to the source. For instance, "Mr. Jones, a metropolitan police captain, said…"
- On background — Information provided "on background" may be attributed to a person's position. For instance, "A metropolitan police worker speaking on condition of anonymity said…"
- Deep background — Information provided "on deep background" may be included in the article, but not clearly attributed. For instance, "A source familiar with the investigation indicated…" or simply "there are suspicions that…"
Lawyers are often required by law to keep confidential anything pertaining to the representation of a client. The duty of confidentiality is much broader than the attorney-client evidentiary privilege, which only covers communications between the attorney and the client.
Both the privilege and the duty serve the purpose of encouraging clients to speak frankly about their cases. This way, lawyers will be able to carry out their duty to provide clients with zealous representation. Otherwise, the opposing side may be able to surprise the lawyer in court with something which he did not know about his client, which makes both lawyer and client look stupid. Also, a distrustful client might hide a relevant fact which he thinks is incriminating (because it shows motive), but which a skilled lawyer could turn to the client's advantage (for example, by raising affirmative defenses like self-defense).
However, most jurisdictions have exceptions for situations where the lawyer knows that the client is about to kill or seriously injure someone, or is using the lawyer's services to perpetuate a crime or fraud. In such situations the lawyer may be able to notify the police, though they usually must first confront the client and try to convince the client to conform his or her conduct to the boundaries of the law.
Note that these exceptions generally do not cover crimes that have already occurred, even in extreme cases where murderers have confessed the location of missing bodies to their lawyers but the police are still looking for those bodies. The U.S. Supreme Court and many state supreme courts have affirmed the right of a lawyer to keep their mouth shut in such situations. Otherwise, it would be impossible for any criminal defendant to obtain a zealous defense.
California is famous for having one of the strongest duties of confidentiality in the world; its lawyers must protect client confidences at "every peril to himself or herself." Until an amendment in 2004, California lawyers could not breach their duty even if they knew that a client was about to commit murder.
Recent legislation in the UK curtails the confidentiality professionals like lawyers and accountants can maintain at the expense of the state. Accountants, for example, are required to disclose to the state any suspicions of fraudulent accounting and, even, the legitimate use of tax saving schemes if those schemes are not already known to the tax authorities.
See also: Physician-patient privilege
Confidentiality is also associated with the relationship between a penitent and their religious advisor. In Roman Catholicism, a priest cannot relate anything revealed in the Sacrament of Reconciliation to a third party, even to save their own life or that of another.