diff --git a/api/requests.http b/api/requests.http
index ac28024..2d922d2 100644
--- a/api/requests.http
+++ b/api/requests.http
@@ -42,12 +42,12 @@ Content-Type: application/json
 
 [
   {
-    "id": "8GHr-tUz6JBRFpTUXDV4w",
-    "state": "Pending",
+    "id": "-rnEaUz7KObDdokPrzKpM",
+    "state": "Delivered",
     "recipients": [
       {
-        "phoneNumber": "79990001234",
-        "state": "Pending"
+        "phoneNumber": "{{phone}}",
+        "state": "Delivered"
       }
     ]
   }
diff --git a/configs/config.example.yml b/configs/config.example.yml
index afcc0a4..bf5e2cb 100644
--- a/configs/config.example.yml
+++ b/configs/config.example.yml
@@ -16,3 +16,6 @@ fcm:
     {
     ...
     }
+tasks:
+  hashing:
+    interval_seconds: 15
diff --git a/internal/config/config.go b/internal/config/config.go
index d820e58..a43a78d 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -4,6 +4,7 @@ type Config struct {
 	HTTP     HTTP      `yaml:"http"`
 	Database Database  `yaml:"database"`
 	FCM      FCMConfig `yaml:"fcm"`
+	Tasks    Tasks     `yaml:"tasks"`
 }
 
 type HTTP struct {
@@ -24,6 +25,14 @@ type FCMConfig struct {
 	CredentialsJSON string `yaml:"credentials_json"`
 }
 
+type Tasks struct {
+	Hashing HashingTask `yaml:"hashing"`
+}
+
+type HashingTask struct {
+	IntervalSeconds uint16 `yaml:"interval_seconds"`
+}
+
 var defaultConfig = Config{
 	HTTP: HTTP{
 		Listen: ":3000",
@@ -40,4 +49,9 @@ var defaultConfig = Config{
 	FCM: FCMConfig{
 		CredentialsJSON: "",
 	},
+	Tasks: Tasks{
+		Hashing: HashingTask{
+			IntervalSeconds: uint16(15 * 60),
+		},
+	},
 }
diff --git a/internal/config/module.go b/internal/config/module.go
index c9da284..442f409 100644
--- a/internal/config/module.go
+++ b/internal/config/module.go
@@ -1,10 +1,13 @@
 package config
 
 import (
+	"time"
+
 	"github.com/capcom6/sms-gateway/internal/infra/config"
 	"github.com/capcom6/sms-gateway/internal/infra/db"
 	"github.com/capcom6/sms-gateway/internal/infra/http"
 	"github.com/capcom6/sms-gateway/internal/sms-gateway/services"
+	"github.com/capcom6/sms-gateway/internal/sms-gateway/tasks"
 	"go.uber.org/fx"
 	"go.uber.org/zap"
 )
@@ -41,4 +44,9 @@ var Module = fx.Module(
 			CredentialsJSON: cfg.FCM.CredentialsJSON,
 		}
 	}),
+	fx.Provide(func(cfg Config) tasks.HashingTaskConfig {
+		return tasks.HashingTaskConfig{
+			Interval: time.Duration(cfg.Tasks.Hashing.IntervalSeconds) * time.Second,
+		}
+	}),
 )
diff --git a/internal/sms-gateway/app.go b/internal/sms-gateway/app.go
index 15585b8..c00cdbd 100644
--- a/internal/sms-gateway/app.go
+++ b/internal/sms-gateway/app.go
@@ -11,6 +11,7 @@ import (
 	"github.com/capcom6/sms-gateway/internal/sms-gateway/models"
 	"github.com/capcom6/sms-gateway/internal/sms-gateway/repositories"
 	"github.com/capcom6/sms-gateway/internal/sms-gateway/services"
+	"github.com/capcom6/sms-gateway/internal/sms-gateway/tasks"
 	"go.uber.org/fx"
 	"go.uber.org/fx/fxevent"
 	"go.uber.org/zap"
@@ -28,6 +29,7 @@ var Module = fx.Module(
 	repositories.Module,
 	models.Module,
 	db.Module,
+	tasks.Module,
 )
 
 func Run() {
diff --git a/internal/sms-gateway/models/migrations/mysql/20231208173729_hashed_messages.sql b/internal/sms-gateway/models/migrations/mysql/20231208173729_hashed_messages.sql
new file mode 100644
index 0000000..3e88dcc
--- /dev/null
+++ b/internal/sms-gateway/models/migrations/mysql/20231208173729_hashed_messages.sql
@@ -0,0 +1,13 @@
+-- +goose Up
+-- +goose StatementBegin
+ALTER TABLE `messages`
+ADD `is_hashed` tinyint(1) unsigned NOT NULL DEFAULT false;
+-- +goose StatementEnd
+-- +goose StatementBegin
+CREATE INDEX `idx_messages_is_hashed` USING HASH ON `messages` (`is_hashed`);
+-- +goose StatementEnd
+---
+-- +goose Down
+-- +goose StatementBegin
+ALTER TABLE `messages` DROP `is_hashed`;
+-- +goose StatementEnd
\ No newline at end of file
diff --git a/internal/sms-gateway/models/models.go b/internal/sms-gateway/models/models.go
index b3b86b3..180394c 100644
--- a/internal/sms-gateway/models/models.go
+++ b/internal/sms-gateway/models/models.go
@@ -51,6 +51,8 @@ type Message struct {
 	SimNumber          *uint8       `gorm:"type:tinyint(1) unsigned"`
 	WithDeliveryReport bool         `gorm:"not null;type:tinyint(1) unsigned"`
 
+	IsHashed bool `gorm:"not null;type:tinyint(1) unsigned;default:0"`
+
 	Device     Device             `gorm:"foreignKey:DeviceID;constraint:OnDelete:CASCADE"`
 	Recipients []MessageRecipient `gorm:"foreignKey:MessageID;constraint:OnDelete:CASCADE"`
 
diff --git a/internal/sms-gateway/repositories/messages.go b/internal/sms-gateway/repositories/messages.go
index 3d0b159..7163988 100644
--- a/internal/sms-gateway/repositories/messages.go
+++ b/internal/sms-gateway/repositories/messages.go
@@ -1,13 +1,16 @@
 package repositories
 
 import (
+	"database/sql"
+	"errors"
+
 	"github.com/capcom6/sms-gateway/internal/sms-gateway/models"
 	"gorm.io/gorm"
 )
 
-var (
-	ErrMessageNotFound = gorm.ErrRecordNotFound
-)
+const HashingLockName = "36444143-1ace-4dbf-891c-cc505911497e"
+
+var ErrMessageNotFound = gorm.ErrRecordNotFound
 
 type MessagesRepository struct {
 	db *gorm.DB
@@ -66,6 +69,35 @@ func (r *MessagesRepository) UpdateState(message *models.Message) error {
 	})
 }
 
+func (r *MessagesRepository) HashProcessed() error {
+	return r.db.Transaction(func(tx *gorm.DB) error {
+		hasLock := sql.NullBool{}
+		lockRow := tx.Raw("SELECT GET_LOCK(?, 1)", HashingLockName).Row()
+		err := lockRow.Scan(&hasLock)
+		if err != nil {
+			return err
+		}
+
+		if !hasLock.Valid || !hasLock.Bool {
+			return errors.New("failed to acquire lock")
+		}
+		defer tx.Exec("SELECT RELEASE_LOCK(?)", HashingLockName)
+
+		err = tx.Model(&models.MessageRecipient{}).
+			Where("message_id IN (?)", tx.Model(&models.Message{}).Select("id").Where("is_hashed = ? AND state <> ?", false, models.MessageStatePending)).
+			Update("phone_number", gorm.Expr("LEFT(SHA2(phone_number, 256), 16)")).
+			Error
+		if err != nil {
+			return err
+		}
+
+		return tx.Model(&models.Message{}).
+			Where("is_hashed = ? AND state <> ?", false, models.MessageStatePending).
+			Updates(map[string]interface{}{"is_hashed": true, "message": gorm.Expr("SHA2(message, 256)")}).
+			Error
+	})
+}
+
 func NewMessagesRepository(db *gorm.DB) *MessagesRepository {
 	return &MessagesRepository{
 		db: db,
diff --git a/internal/sms-gateway/services/messages.go b/internal/sms-gateway/services/messages.go
index 48fffc6..3b80237 100644
--- a/internal/sms-gateway/services/messages.go
+++ b/internal/sms-gateway/services/messages.go
@@ -2,6 +2,7 @@ package services
 
 import (
 	"context"
+	"crypto/sha256"
 	"errors"
 	"fmt"
 	"log"
@@ -85,7 +86,7 @@ func (s *MessagesService) UpdateState(deviceID string, message smsgateway.Messag
 	}
 
 	existing.State = models.MessageState(message.State)
-	existing.Recipients = s.recipientsStateToModel(message.Recipients)
+	existing.Recipients = s.recipientsStateToModel(message.Recipients, existing.IsHashed)
 
 	return s.Messages.UpdateState(&existing)
 }
@@ -163,6 +164,10 @@ func (s *MessagesService) Enqeue(device models.Device, message smsgateway.Messag
 	return state, nil
 }
 
+func (s *MessagesService) HashProcessed() error {
+	return s.Messages.HashProcessed()
+}
+
 func (s *MessagesService) filterTimeouted(messages []models.Message) []models.Message {
 	result := make([]models.Message, 0, len(messages))
 	for _, v := range messages {
@@ -202,12 +207,13 @@ func (s *MessagesService) recipientsToModel(input []string) []models.MessageReci
 	return output
 }
 
-func (s *MessagesService) recipientsStateToModel(input []smsgateway.RecipientState) []models.MessageRecipient {
+func (s *MessagesService) recipientsStateToModel(input []smsgateway.RecipientState, hash bool) []models.MessageRecipient {
 	output := make([]models.MessageRecipient, len(input))
 
 	for i, v := range input {
 		phoneNumber := v.PhoneNumber
 		if len(phoneNumber) > 0 && phoneNumber[0] != '+' {
+			// compatibility with Android app before 1.1.1
 			phoneNumber = "+" + phoneNumber
 		}
 
@@ -215,6 +221,10 @@ func (s *MessagesService) recipientsStateToModel(input []smsgateway.RecipientSta
 			v.State = smsgateway.MessageStateProcessed
 		}
 
+		if hash {
+			phoneNumber = fmt.Sprintf("%x", sha256.Sum256([]byte(phoneNumber)))[:16]
+		}
+
 		output[i] = models.MessageRecipient{
 			PhoneNumber: phoneNumber,
 			State:       models.MessageState(v.State),
diff --git a/internal/sms-gateway/services/messages_test.go b/internal/sms-gateway/services/messages_test.go
index 7714f72..b2aa266 100644
--- a/internal/sms-gateway/services/messages_test.go
+++ b/internal/sms-gateway/services/messages_test.go
@@ -11,6 +11,7 @@ import (
 func TestMessagesService_recipientsStateToModel(t *testing.T) {
 	type args struct {
 		input []smsgateway.RecipientState
+		hash  bool
 	}
 	tests := []struct {
 		name string
@@ -56,6 +57,26 @@ func TestMessagesService_recipientsStateToModel(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "With hashing",
+			s:    &MessagesService{},
+			args: args{
+				input: []smsgateway.RecipientState{
+					{
+						PhoneNumber: "+79990001234",
+						State:       "",
+					},
+				},
+				hash: true,
+			},
+			want: []models.MessageRecipient{
+				{
+					MessageID:   0,
+					PhoneNumber: "62d17792b45c5307",
+					State:       "",
+				},
+			},
+		},
 		{
 			name: "Empty phone",
 			s:    &MessagesService{},
@@ -78,7 +99,7 @@ func TestMessagesService_recipientsStateToModel(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := tt.s.recipientsStateToModel(tt.args.input); !reflect.DeepEqual(got, tt.want) {
+			if got := tt.s.recipientsStateToModel(tt.args.input, tt.args.hash); !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("MessagesService.recipientsStateToModel() = %v, want %v", got, tt.want)
 			}
 		})
diff --git a/internal/sms-gateway/tasks/hashing.go b/internal/sms-gateway/tasks/hashing.go
new file mode 100644
index 0000000..0ebe5d5
--- /dev/null
+++ b/internal/sms-gateway/tasks/hashing.go
@@ -0,0 +1,52 @@
+package tasks
+
+import (
+	"context"
+	"time"
+
+	"github.com/capcom6/sms-gateway/internal/sms-gateway/services"
+	"go.uber.org/fx"
+	"go.uber.org/zap"
+)
+
+type HashingTaskConfig struct {
+	Interval time.Duration
+}
+
+type HashingTaskParams struct {
+	fx.In
+
+	MessagesSvc *services.MessagesService
+	Config      HashingTaskConfig
+	Logger      *zap.Logger
+}
+
+type HashingTask struct {
+	MessagesSvc *services.MessagesService
+	Config      HashingTaskConfig
+	Logger      *zap.Logger
+}
+
+func (t *HashingTask) Run(ctx context.Context) {
+	t.Logger.Info("Starting hashing task...")
+	for {
+		select {
+		case <-ctx.Done():
+			t.Logger.Info("Stopping hashing task...")
+			return
+		case <-time.After(t.Config.Interval):
+			t.Logger.Debug("Hashing messages...")
+			if err := t.MessagesSvc.HashProcessed(); err != nil {
+				t.Logger.Error("Failed to hash processed messages", zap.Error(err))
+			}
+		}
+	}
+}
+
+func NewHashingTask(params HashingTaskParams) *HashingTask {
+	return &HashingTask{
+		MessagesSvc: params.MessagesSvc,
+		Config:      params.Config,
+		Logger:      params.Logger,
+	}
+}
diff --git a/internal/sms-gateway/tasks/module.go b/internal/sms-gateway/tasks/module.go
new file mode 100644
index 0000000..c0df981
--- /dev/null
+++ b/internal/sms-gateway/tasks/module.go
@@ -0,0 +1,37 @@
+package tasks
+
+import (
+	"context"
+
+	"go.uber.org/fx"
+	"go.uber.org/zap"
+)
+
+var Module = fx.Module(
+	"tasks",
+	fx.Decorate(func(log *zap.Logger) *zap.Logger {
+		return log.Named("tasks")
+	}),
+	fx.Provide(
+		NewHashingTask,
+		fx.Private,
+	),
+	fx.Invoke(
+		func(lc fx.Lifecycle, task *HashingTask) error {
+			ctx, cancel := context.WithCancel(context.Background())
+
+			lc.Append(fx.Hook{
+				OnStart: func(_ context.Context) error {
+					go task.Run(ctx)
+					return nil
+				},
+				OnStop: func(_ context.Context) error {
+					cancel()
+					return nil
+				},
+			})
+
+			return nil
+		},
+	),
+)