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STATUS_EFS_ALG_BLOB_TOO_BIG
The destination cannot represent the source EFS algorithm data
EFS metadata includes algorithm and key-wrapping information needed to protect the file-encryption key. This status can occur when copying or transforming an encrypted file between implementations whose metadata buffers or supported algorithms differ.
The failure is not solved by truncating the blob. Doing so would make the cryptographic metadata unusable. Keep the source intact and use an EFS-aware export, decrypt-and-reencrypt workflow, or compatible destination that can represent the algorithm information.
What to inspect
- Record source and destination Windows versions, file systems, providers, and EFS algorithm metadata.
- Verify that the destination supports the source encryption and key-wrapping format.
- Perform migration on a copy and validate decryption before retiring the original encrypted file.
References
- Microsoft Open Specifications: EFSRPC
- Microsoft Open Specifications: Encrypting File System overview
- Microsoft: EFS file and recovery keys
- libyal: NTFS format documentation
- Microsoft Open Specifications: NTSTATUS values
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