Ist ein verschlüsseltes Bitlocker-Laufwerk sicher zu entsorgen?

You are disposing of a drive and want to ensure the data is not leaked.

If the data was stored in plain-text (i.e. not encrypted), you would have to ensure the data was 'shredded'. Just formatting the drive would not be sufficient; formatting doesn't overwrite the data, which is why there are 'unformat' utilities.

Instead, you'd consider a tool like DBAN. There are various erasure standards and as @Raystafarian points out, you can be all but sure the data is unrecoverable if you do a 7-pass shred. In truth, there are no reports of successful recovery after even a single pass on a modern mechanical hard drive, but it often pays to be conservative.

Matters are more complicated when considering SSDs. See this article (thanks to @Raystafarian for the link) for more information. SSDs remap blocks, which means you can overwrite all the data on the drive and some of the old data may have been remapped and not actually overwritten. DBAN doesn't handle SSDs.

Okay, but this isn't what you are doing. You have stored the data protected using Bitlocker and aren't planning on shredding or even overwriting the data at all. What you are suggesting is actually similar to how SSDs often implement 'secure erase'. They encrypt all data and then, during the 'secure erase', simply overwrite the block containing the key. Without the key, there's no practical way to recover the data.

This is true in your case, too. You cannot recover the data from a Bitlocker-encrypted drive without knowing the key, assuming no vulnerabilities in the Bitlocker implementation or in the underlying encryption algorithm. The fact that you know a great deal of the plain-text ("known Windows files or known data structures") is irrelevant; the encryption algorithm is strong despite known plaintexts.

In this case, against most adversaries, I'd suggest just doing a complete (as opposed to a quick) format. Even that shouldn't be necessary, but it's probably a good plan. Against a well-funded government or evil criminal empire? Well, you probably have other problems. And then I'd definitely be wiping the drive (using DBAN or a similar SSD-capable tool) and physically destroying the drive.

Der Vollständigkeit halber können Sie, abhängig von der Zerstörung von Daten, die NIST Special Publication 800-88 Richtlinien für Mediensanierung beachten. Ab Seite 26 finden Sie in Anhang A - Empfehlungen zur minimalen Hygienemaßnahme, die Tabelle A-1 zur Reinigung von Hard Copy-Speichern enthält .

Auf dem Tisch zusammengefasst ist eine nicht umfassende Liste von Clear-, Bereinigungs- und Zerstörungsmethoden. Eine Mindestempfehlung für das Clearing lautet

Mindestens ein Durchlauf von Schreibvorgängen mit einem festen Datenwert wie Nullen. Alternativ können mehrere Durchgänge oder komplexere Werte verwendet werden

Dies beinhaltet jegliche vorhandene Verschlüsselung. "Sicher zu entsorgen" würde also nicht nur durch bitlocker qualifiziert. Und die Empfehlung zu zerstören ist

zerkleinern, zerfallen, pulverisieren oder verbrennen.

Dies sind Mindestanforderungen, die vom National Institute of Standards and Technology empfohlen werden. Wenn Sie keine PII-, PCI-, PHI-, proprietären oder anderweitig sensiblen Daten haben, müssen Sie sich nicht darum kümmern.

Berücksichtigen Sie auch meinen Hintergrund der Informationssicherheit und meinen Alufolie-Hut.

Chris gave a nicely comprehensive answer. His advice—particularly on encrypting, securely deleting and if necessary destroying—is sound. As others have mentioned the question depends on your expected adversary and the value of the data. Two corollaries:

1. Computer forensics has developed at a truly astonishing rate. It is difficult to overestime the capabilities of even modest companies.

2. Bitlocker is closed source. Any faith placed in Bitlocker to be effective is solely based upon the trust of Microsoft and its partners with NDAs who have audited the source code. I have now idea what it does, you have no idea what it does and neither does much of the security community (the one's that do can't tell you). Whether or not there are 'backdoors' or weaknesses that can be exploited is speculation, and that's the problem. Its effectiveness is an unknown quantity, one that is anecdotal rather than rigourous.

supposing the user thinks the Bitlocker password is strong enough to make bruteforce unviable with the current technology

This is a supposition which is by its nature unfounded. It will again be dependant upon the nature of the adversary.

This is a question that involves security and the confidentiality and integrity of data. For you (and most) it may be a question of learning more about the technology. For others reading the question it may well be a matter of life and death. As such anyone reading should be sure to do their research, identify security experts and data security policies used where the highest care is taken and do their best to implement them.

So in answer to

is the bypass process all about plain bruteforce, or are there known factors which make the process easier?

From the few attacks we've seen published the encryption is bypassed, not broken. It is unknown whether Microsoft or certain Governments have extant side-channel (or other) attacks against Bitlocker; the removal of a component called the elephant diffuser was taken to be a net weakening of the system and could be seen as a precendent for such behaviour.

This question would probably also benefit from being asked on the information security stackexchange.