github.com/dahs81/otto@v0.2.1-0.20160126165905-6400716cf085/website/source/docs/concepts/seal.html.md (about)

     1  ---
     2  layout: "docs"
     3  page_title: "Seal/Unseal"
     4  sidebar_current: "docs-concepts-seal"
     5  description: |-
     6    A Vault must be unsealed before it can access its data. Likewise, it can be sealed to lock it down.
     7  ---
     8  
     9  # Seal/Unseal
    10  
    11  When a Vault server is started, it starts in a _sealed_ state. In this
    12  state, Vault is configured to know where and how to access the physical
    13  storage, but doesn't know how to decrypt any of it.
    14  
    15  _Unsealing_ is the process of constructing the master key necessary to
    16  read the decryption key to decrypt the data, allowing access to the Vault.
    17  
    18  Prior to unsealing, almost no operations are possible with Vault. For
    19  example authentication, managing the mount tables, etc. are all not possible.
    20  The only possible operations are to unseal the Vault and check the status
    21  of the unseal.
    22  
    23  ## Why?
    24  
    25  The data stored by Vault is stored encrypted. Vault needs the
    26  _encryption key_ in order to decrypt the data. The encryption key is
    27  also stored with the data, but encrypted with another encryption key
    28  known as the _master key_. The master key isn't stored anywhere.
    29  
    30  Therefore, to decrypt the data, Vault must decrypt the encryption key
    31  which requires the master key. Unsealing is the process of reconstructing
    32  this master key.
    33  
    34  Instead of distributing this master key as a single key to an operator,
    35  Vault uses an algorithm known as
    36  [Shamir's Secret Sharing](http://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing)
    37  to split the key into shards. A certain threshold of shards is required to
    38  reconstruct the master key.
    39  
    40  This is the _unseal_ process: the shards are added one at a time (in any
    41  order) until enough shards are present to reconstruct the key and
    42  decrypt the data.
    43  
    44  ## Unsealing
    45  
    46  The unseal process is done by running `vault unseal` or via the API.
    47  This process is stateful: each key can be entered via multiple mechanisms
    48  on multiple computers and it will work. This allows each shard of the master
    49  key to be on a distinct machine for better security.
    50  
    51  Once a Vault is unsealed, it remains unsealed until one of two things happens:
    52  
    53    1. It is resealed via the API (see below).
    54  
    55    2. The server is restarted.
    56  
    57  -> **Note:** Unsealing makes the process of automating a Vault install
    58  difficult. Automated tools can easily install, configure, and start Vault,
    59  but unsealing it is a very manual process. We have plans in the future to
    60  make it easier. For the time being, the best method is to manually unseal
    61  multiple Vault servers in [HA mode](/docs/concepts/ha.html). Use a tool such
    62  as Consul to make sure you only query Vault servers that are unsealed.
    63  
    64  ## Sealing
    65  
    66  There is also an API to seal the Vault. This will throw away the encryption
    67  key and require another unseal process to restore it. Sealing only requires
    68  a single operator with root privileges.
    69  
    70  This way, if there is a detected intrusion, the Vault data can be locked
    71  quickly to try to minimize damages. It can't be accessed again without
    72  access to the master key shards.