diff --git a/res/css/views/dialogs/security/_AccessSecretStorageDialog.scss b/res/css/views/dialogs/security/_AccessSecretStorageDialog.scss
index 63d0ca555d..30b79c1a9a 100644
--- a/res/css/views/dialogs/security/_AccessSecretStorageDialog.scss
+++ b/res/css/views/dialogs/security/_AccessSecretStorageDialog.scss
@@ -1,6 +1,5 @@
 /*
-Copyright 2018 New Vector Ltd
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2018, 2019, 2021 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,6 +14,27 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+.mx_AccessSecretStorageDialog_reset {
+    position: relative;
+    padding-left: 24px; // 16px icon + 8px padding
+    margin-top: 7px; // vertical alignment to buttons
+
+    &::before {
+        content: "";
+        display: inline-block;
+        position: absolute;
+        height: 16px;
+        width: 16px;
+        left: 0;
+        top: 2px; // alignment
+        background-image: url("$(res)/img/element-icons/warning-badge.svg");
+    }
+
+    .mx_AccessSecretStorageDialog_reset_link {
+        color: $warning-color;
+    }
+}
+
 .mx_AccessSecretStorageDialog_titleWithIcon::before {
     content: '';
     display: inline-block;
@@ -26,6 +46,13 @@ limitations under the License.
     background-color: $primary-fg-color;
 }
 
+.mx_AccessSecretStorageDialog_resetBadge::before {
+    // The image isn't capable of masking, so we use a background instead.
+    background-image: url("$(res)/img/element-icons/warning-badge.svg");
+    background-size: 24px;
+    background-color: transparent;
+}
+
 .mx_AccessSecretStorageDialog_secureBackupTitle::before {
     mask-image: url('$(res)/img/feather-customised/secure-backup.svg');
 }
diff --git a/src/Modal.tsx b/src/Modal.tsx
index ab582b9b22..ce11c571b6 100644
--- a/src/Modal.tsx
+++ b/src/Modal.tsx
@@ -36,6 +36,7 @@ export interface IModal<T extends any[]> {
     onBeforeClose?(reason?: string): Promise<boolean>;
     onFinished(...args: T): void;
     close(...args: T): void;
+    hidden?: boolean;
 }
 
 export interface IHandle<T extends any[]> {
@@ -93,6 +94,12 @@ export class ModalManager {
         return container;
     }
 
+    public toggleCurrentDialogVisibility() {
+        const modal = this.getCurrentModal();
+        if (!modal) return;
+        modal.hidden = !modal.hidden;
+    }
+
     public hasDialogs() {
         return this.priorityModal || this.staticModal || this.modals.length > 0;
     }
@@ -364,7 +371,7 @@ export class ModalManager {
         }
 
         const modal = this.getCurrentModal();
-        if (modal !== this.staticModal) {
+        if (modal !== this.staticModal && !modal.hidden) {
             const classes = classNames("mx_Dialog_wrapper", modal.className, {
                 mx_Dialog_wrapperWithStaticUnder: this.staticModal,
             });
diff --git a/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx b/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
index 3c09470b39..283e4208a6 100644
--- a/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
+++ b/src/components/views/dialogs/security/AccessSecretStorageDialog.tsx
@@ -25,6 +25,8 @@ import Field from '../../elements/Field';
 import AccessibleButton from '../../elements/AccessibleButton';
 import {_t} from '../../../../languageHandler';
 import {IDialogProps} from "../IDialogProps";
+import {accessSecretStorage} from "../../../../SecurityManager";
+import Modal from "../../../../Modal";
 
 // Maximum acceptable size of a key file. It's 59 characters including the spaces we encode,
 // so this should be plenty and allow for people putting extra whitespace in the file because
@@ -47,6 +49,7 @@ interface IState {
     forceRecoveryKey: boolean;
     passPhrase: string;
     keyMatches: boolean | null;
+    resetting: boolean;
 }
 
 /*
@@ -66,10 +69,14 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
             forceRecoveryKey: false,
             passPhrase: '',
             keyMatches: null,
+            resetting: false,
         };
     }
 
     private onCancel = () => {
+        if (this.state.resetting) {
+            this.setState({resetting: false});
+        }
         this.props.onFinished(false);
     };
 
@@ -201,6 +208,50 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
         });
     };
 
+    private onResetAllClick = (ev: React.MouseEvent<HTMLAnchorElement>) => {
+        ev.preventDefault();
+        this.setState({resetting: true});
+    };
+
+    private onConfirmResetAllClick = async () => {
+        // Hide ourselves so the user can interact with the reset dialogs.
+        // We don't conclude the promise chain (onFinished) yet to avoid confusing
+        // any upstream code flows.
+        //
+        // Note: this will unmount us, so don't call `setState` or anything in the
+        // rest of this function.
+        Modal.toggleCurrentDialogVisibility();
+
+        // Force reset secret storage (which resets the key backup)
+        await accessSecretStorage(async () => {
+            // Now reset cross-signing so everything Just Works™ again.
+            const cli = MatrixClientPeg.get();
+            await cli.bootstrapCrossSigning({
+                authUploadDeviceSigningKeys: async (makeRequest) => {
+                    // XXX: Making this an import breaks the app.
+                    const InteractiveAuthDialog = sdk.getComponent("views.dialogs.InteractiveAuthDialog");
+                    const { finished } = Modal.createTrackedDialog(
+                        'Cross-signing keys dialog', '', InteractiveAuthDialog,
+                        {
+                            title: _t("Setting up keys"),
+                            matrixClient: cli,
+                            makeRequest,
+                        },
+                    );
+                    const [confirmed] = await finished;
+                    if (!confirmed) {
+                        throw new Error("Cross-signing key upload auth canceled");
+                    }
+                },
+                setupNewCrossSigning: true,
+            });
+
+            // Now we can indicate that the user is done pressing buttons, finally.
+            // Upstream flows will detect the new secret storage, key backup, etc and use it.
+            this.props.onFinished(true);
+        }, true);
+    };
+
     private getKeyValidationText(): string {
         if (this.state.recoveryKeyFileError) {
             return _t("Wrong file type");
@@ -216,8 +267,9 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
     }
 
     render() {
-        // Caution: Making this an import will break tests.
+        // Caution: Making these an import will break tests.
         const BaseDialog = sdk.getComponent("views.dialogs.BaseDialog");
+        const DialogButtons = sdk.getComponent("views.elements.DialogButtons");
 
         const hasPassphrase = (
             this.props.keyInfo &&
@@ -226,11 +278,36 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
             this.props.keyInfo.passphrase.iterations
         );
 
+        const resetButton = (
+            <div className="mx_AccessSecretStorageDialog_reset">
+                {_t("Forgotten or lost all recovery methods? <a>Reset all</a>", null, {
+                    a: (sub) => <a
+                        href="" onClick={this.onResetAllClick}
+                        className="mx_AccessSecretStorageDialog_reset_link">{sub}</a>,
+                })}
+            </div>
+        );
+
         let content;
         let title;
         let titleClass;
-        if (hasPassphrase && !this.state.forceRecoveryKey) {
-            const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
+        if (this.state.resetting) {
+            title = _t("Reset everything");
+            titleClass = ['mx_AccessSecretStorageDialog_titleWithIcon mx_AccessSecretStorageDialog_resetBadge'];
+            content = <div>
+                <p>{_t("Only do this if you have no other device to complete verification with.")}</p>
+                <p>{_t("If you reset everything, you will restart with no trusted devices, no trusted users, and "
+                    + "might not be able to see past messages.")}</p>
+                <DialogButtons
+                    primaryButton={_t('Reset')}
+                    onPrimaryButtonClick={this.onConfirmResetAllClick}
+                    hasCancel={true}
+                    onCancel={this.onCancel}
+                    focus={false}
+                    primaryButtonClass="danger"
+                />
+            </div>;
+        } else if (hasPassphrase && !this.state.forceRecoveryKey) {
             const AccessibleButton = sdk.getComponent('elements.AccessibleButton');
             title = _t("Security Phrase");
             titleClass = ['mx_AccessSecretStorageDialog_titleWithIcon mx_AccessSecretStorageDialog_securePhraseTitle'];
@@ -278,13 +355,13 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
                         onCancel={this.onCancel}
                         focus={false}
                         primaryDisabled={this.state.passPhrase.length === 0}
+                        additive={resetButton}
                     />
                 </form>
             </div>;
         } else {
             title = _t("Security Key");
             titleClass = ['mx_AccessSecretStorageDialog_titleWithIcon mx_AccessSecretStorageDialog_secureBackupTitle'];
-            const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
 
             const feedbackClasses = classNames({
                 'mx_AccessSecretStorageDialog_recoveryKeyFeedback': true,
@@ -339,6 +416,7 @@ export default class AccessSecretStorageDialog extends React.PureComponent<IProp
                         onCancel={this.onCancel}
                         focus={false}
                         primaryDisabled={!this.state.recoveryKeyValid}
+                        additive={resetButton}
                     />
                 </form>
             </div>;
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 0668f54822..9592d1360d 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -2369,6 +2369,10 @@
     "Looks good!": "Looks good!",
     "Wrong Security Key": "Wrong Security Key",
     "Invalid Security Key": "Invalid Security Key",
+    "Forgotten or lost all recovery methods? <a>Reset all</a>": "Forgotten or lost all recovery methods? <a>Reset all</a>",
+    "Reset everything": "Reset everything",
+    "Only do this if you have no other device to complete verification with.": "Only do this if you have no other device to complete verification with.",
+    "If you reset everything, you will restart with no trusted devices, no trusted users, and might not be able to see past messages.": "If you reset everything, you will restart with no trusted devices, no trusted users, and might not be able to see past messages.",
     "Security Phrase": "Security Phrase",
     "Unable to access secret storage. Please verify that you entered the correct Security Phrase.": "Unable to access secret storage. Please verify that you entered the correct Security Phrase.",
     "Enter your Security Phrase or <button>Use your Security Key</button> to continue.": "Enter your Security Phrase or <button>Use your Security Key</button> to continue.",