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+# Introduction of Gradido-ID
+
+## Motivation
+
+To introduce the Gradido-ID base on the requirement to identify an user account per technical key instead of using an email-address. Such a technical key ensures an exact identification of an user account without giving detailed information for possible missusage.
+
+Additionally the Gradido-ID allows to administrade any user account data like changing the email address or define several email addresses without any side effects on the identification of the user account.
+
+## Definition
+
+The definition of the Gradido-ID can be found in the document [BenutzerVerwaltung#Gradido-ID](../BusinessRequirements/BenutzerVerwaltung#Gradido-ID).
+
+## Steps of Introduction
+
+To Introduce the Gradido-ID there are several steps necessary. The first step is to define a proper database schema with additional columns and tables followed by data migration steps to add or initialize the new columns and tables by keeping valid data at all.
+
+The second step is to decribe all concerning business logic processes, which have to be adapted by introducing the Gradido-ID.
+
+### Database-Schema
+
+#### Users-Table
+
+##### new Columns
+
+The database entity *Users* has to be extended by the new columns:
+
+###### Gradido-ID
+
+the technical key of the user as UUID
+
+```
+@Column({ length: 36, unique: true, nullable: false })
+  Gradido-ID: string
+```
+
+###### Alias
+
+an alias as business key of the user
+
+```
+@Column({ length: 255, unique: true, nullable: true, collation: 'utf8mb4_unicode_ci' })
+  alias: string
+```
+
+###### Passphrase_Encryption_Type
+
+defines the type of encrypting the passphrase: 1 = email (default), 2 = gradidoID, ...
+
+```
+@Column({ type: 'int', default: 1, unique: false, nullable: false })
+passphrase_encryption_type: int
+```
+
+##### changed Columns
+
+###### Email
+
+the existing column email, will now be changed to the primary email contact, which will be stored as a contact entry in the new contact table. It is necessary to decide if the content of this column will be changed to a foreign key to the contact entry with the email address or if the email itself will be kept as a denormalized and duplicate value in the users table.
+
+The preferred and proper solution will be to add a new column emailId as foreign key to the contact entry and delete the email column after the migration of the email address in the contact table.
+
+```
+  @Column({ name: 'eamil_id', unsigned: true, nullable: false })
+  emailId: number
+
+replaces the following column:
+
+  @Column({ length: 255, unique: true, nullable: false, collation: 'utf8mb4_unicode_ci' })
+  email: string
+
+```
+
+#### new Contact-Table
+
+A new entity is introduced to store several contacts of different types like email, telephone or other kinds of contact addresses.
+
+```
+@Entity('user_contacts', { engine: 'InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci' })
+export class UserContacts extends BaseEntity {
+```
+
+###### Id
+
+the technical key of a contact entity
+
+```
+@PrimaryGeneratedColumn('increment', { unsigned: true })
+id: number
+```
+
+###### Type
+
+Defines the type of contact entry as enum: Email, Phone, etc
+
+```
+  @Column({ name: 'type', unsigned: true, nullable: false })
+  type: number
+```
+
+###### UserId
+
+Defines the foreign key to the users table
+
+```
+  @Column({ name: 'user_id', unsigned: true, nullable: false })
+  userId: number
+```
+
+###### Email
+
+defines the address of a contact entry of type Email
+
+```
+  @Column({ length: 255, unique: true, nullable: false, collation: 'utf8mb4_unicode_ci' })
+  email: string
+```
+
+###### Phone
+
+defines the address of a contact entry of type Phone
+
+```
+  @Column({ length: 255, unique: true, nullable: false, collation: 'utf8mb4_unicode_ci' })
+  phone: string
+```
+
+###### UsedChannel
+
+define the contact channel for which this entry is confirmed by the user e.g. main address (default), infomail, contracting, advertisings, ...
+
+```
+  @Column({ length: 255, unique: true, nullable: false, collation: 'utf8mb4_unicode_ci' })
+  usedChannel: string
+```
+
+### Database-Migration
+
+After the adaption of the database schema and to keep valid data there must be several steps of data migration to initialize the new and changed columns and tables.
+
+#### Initialize GradidoID
+
+In a one-time migration create for each entry of the users tabel an unique UUID (version4).
+
+#### Primary Email Contact
+
+In a one-time migration read for each entry of the users table the users.id and users.email and create for it a new entry in the contact table, by initializing the contact-values with:
+
+* Id = new technical key
+* Type = Email
+* UserId = users.Id
+* Email = users.email
+* Phone = null
+* UsedChannel = "main address"
+
+and update the users entry with users.emailId = contact.Id
+
+After this one-time migration the column users.email can be deleted.
+
+### Adaption of BusinessLogic
+
+#### Read-Write Access of Users-Table especially Email
+
+#### Registration Process
+
+#### Login Process
+
+#### Password En/Decryption
+
+#### Identity-Mapping