There is a copy of table structure in the InnoDB dictionary (in ibdata1).
The sys_parser tool from Undrop-for-InnoDB (https://twindb.com/data-recovery-toolkit/) reads SYS_TABLES, SYS_INDEXES, SYS_COLUMNS, and SYS_FIELDS and reconstructs a CREATE TABLE statement.
After you compile the tool parse ibdata1 to generate SYS_* dumps:
./stream_parser -f /var/lib/mysql/ibdata1
There is a helper script ./recover_dictionary.sh that loads SYS_* tables in a local MySQL instance. Try to use it, but make sure mysql can connect w/o password.
Then you can generate table schema
# ./sys_parser -u root -p qwerty sakila/actor
CREATE TABLE `actor`(
`actor_id` SMALLINT UNSIGNED NOT NULL,
`first_name` VARCHAR(45) CHARACTER SET 'utf8' COLLATE 'utf8_general_ci' NOT NULL,
`last_name` VARCHAR(45) CHARACTER SET 'utf8' COLLATE 'utf8_general_ci' NOT NULL,
`last_update` TIMESTAMP NOT NULL,
PRIMARY KEY (`actor_id`)
) ENGINE=InnoDB;
See more detailed guide on
https://twindb.com/recover-table-structure-from-innodb-dictionary/
Now, having the CREATE statement you can generate the .frm file and replace it instead of the encrypted one.