Can Hackers Read Encrypted Data Without Stealing the Encryption Key?

Yes. An attacker can read encrypted data without extracting its key if they compromise an application, account, or operating system that already has permission to decrypt it. The system performs the decryption, and the attacker receives the readable result. OWASP recommends protecting encrypted information with additional security layers, including access controls, because encryption alone does not prevent unauthorized application access.

Consider a customer database stored on an encrypted server disk. When an authorized application requests a customer record, the storage system decrypts the relevant data and the database returns it. An attacker who takes over that application may be able to make the same requests. The disk remains encrypted, but the attacker reads records through the running service rather than decrypting a stolen disk image. The encryption layer matters: OWASP notes that filesystem or hardware encryption does not protect against a remotely compromised server in the same way it protects against physical theft.

The same principle applies to an account with permission to view sensitive information. If an attacker gains access to that account, the application may display documents, retrieve records, or generate exports on their behalf. The attacker does not need the underlying encryption key because the service already handles decryption. Whether this succeeds depends on authorization checks, account permissions, and controls around sensitive operations.

HTTPS protects information while it travels between endpoints. At the receiving endpoint, the application must access readable content to process the request. Malware on that endpoint may target the information after decryption rather than attack the encrypted network connection. Infostealer malware follows this broader pattern by collecting sensitive information from infected devices, including credentials and other locally accessible data.

Hardware-protected keys reduce the risk of raw key extraction, but applications still need permission to request cryptographic operations. If a compromised application can submit an authorized decryption request and receive plaintext, keeping the key non-exportable does not stop that particular disclosure. Separating keys from data is valuable, but the permissions governing key use and access to decrypted results remain essential.

The useful distinction is between key theft and plaintext access. Key theft can let an attacker decrypt copied ciphertext independently. Plaintext access lets them obtain readable information through a compromised system while that access remains available. A security assessment should examine both: who can obtain the key, and who can make the system decrypt data for them.